31 (thirty-one) is the natural number following 30 and preceding 32. In mathematics, a natural number can mean either an element of the set {1, 2, 3, ...} (i. ... 30 (thirty) is the natural number following 29 and preceding 31. ... 32 is the natural number following 31 and preceding 33. ...

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Aleph-0, the smallest infinite cardinal In mathematics, cardinal numbers, or cardinals for short, are a generalized kind of number used to denote the size of a set, known as its cardinality. ... In set theory, ordinal, ordinal number, and transfinite ordinal number refer to a type of number introduced by Georg Cantor in 1897, to accommodate infinite sequences and to classify sets with certain kinds of order structures on them. ... ... In mathematics, a prime number (or a prime) is a natural number which has exactly two distinct natural number divisors: 1 and itself. ... In mathematics, a divisor of an integer n, also called a factor of n, is an integer which evenly divides n without leaving a remainder. ... The system of Roman numerals is a numeral system originating in ancient Rome, and was adapted from Etruscan numerals. ... The binary numeral system, or base-2 number system, is a numeral system that represents numeric values using two symbols, usually 0 and 1. ... In mathematics and computer science, hexadecimal, base-16, or simply hex, is a numeral system with a radix, or base, of 16, usually written using the symbols 0–9 and A–F, or a–f. ... Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ...

In mathematics

Thirty-one is the third Mersenne prime ( 2⁵ - 1 ) as well as the fourth primorial prime, and together with twenty-nine, another primorial prime, it comprises a twin prime. As a Mersenne prime, 31 is related to the perfect number 496, since 496 = 2^{5 - 1} ( 2⁵ - 1). 31 is the eighth Mersenne prime exponent. 31 is also the 4th lucky prime and the 11th supersingular prime. In mathematics, a Mersenne number is a number that is one less than a power of two. ... In mathematics, primorial primes are prime numbers of the form pn# Â± 1, where: pn# is the primorial of pn. ... 29 (twenty-nine) is the natural number following 28 and preceding 30. ... A twin prime is a prime number that differs from another prime number by two. ... In mathematics, a perfect number is defined as an integer which is the sum of its proper positive divisors, that is, the sum of the positive divisors not including the number. ... Four hundred and ninety-six is the natural number following four hundred and ninety-five and preceding four hundred and ninety-seven. ... In mathematics, a Mersenne number is a number that is one less than a power of two. ... Headline text A lucky prime is a number that is a prime number and a lucky number. ... In mathematics, a supersingular prime is a certain kind of prime number. ...

31 is a centered triangular number, a centered pentagonal number and centered decagonal number. A centered triangular number is a centered figurate number that represents a triangle with a dot in the center and all other dots surrounding the center in successive triangular layers. ... A centered pentagonal number is a centered figurate number that represents a pentagon with a dot in the center and all other dots surrounding the center in successive pentagonal layers. ... A centered decagonal number is a centered figurate number that represents a decagon with a dot in the center and all other dots surrounding the center dot in successive decagonal layers. ...

At 31, the Mertens function sets a new low of -4, a value which is not subceded until 110. In number theory, the Mertens function is where μ(k) is the Möbius function. ... 110 (one hundred [and] ten) is the natural number following 109 and preceding 111. ...

No integer added up to its base 10 digits results in 31, making 31 a self number. A self number or Colombian number is an integer which, in a given base, can not be generated by any other integer added to the sum of its digits. ...

31 is a repdigit in base 5 (111), and base 2 (11111). In recreational mathematics, a repdigit is a natural number composed of repeated instances of the same digit, most often in the decimal numeral system. ...

The numbers 31, 331, 3331, 33331, 333331, 3333331, and 33333331 are all prime. For a time it was thought that every number of the form 3_w1 would be prime. However, the next nine numbers of the sequence are composite; their factorisations are: A composite number is a positive integer which has a positive divisor other than one or itself. ... This article is about the mathematical concept. ...

• 333333331 = 17*19607843
• 3333333331 = 673*4952947
• 33333333331 = 307*108577633
• 333333333331 = 19*83*211371803
• 3333333333331 = 523*3049*2090353
• 33333333333331 = 607*1511*1997*18199
• 333333333333331 = 181*1841620626151
• 3333333333333331 = 199*16750418760469
• 33333333333333331 = 31*1499*717324094199

The recurrence of the factor 31 in the last number above can be used to prove that no sequence of the type R_wE or ER_w can consist only of primes because every prime in the sequence will periodically divide further numbers. Here, 31 divides every fifteenth number in 3_w1 (and 331 every 110th). 17 (seventeen) is the natural number following 16 and preceding 18. ... 19 (nineteen) is the natural number following 18 and preceding 20. ... 83 (eighty-three) is the natural number following 82 and preceding 84. ... 181 is the natural number between 180 and 182. ... 199 is the natural number between 198 and 200. ...

In science

• The atomic number of gallium

See also: List of elements by atomic number In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. ... Not to be confused with Galium. ...

Astronomy

• Messier object M31, a magnitude 4.5 galaxy in the constellation Andromeda. It is also known as the Andromeda Galaxy, and is readily visible to the naked eye in a modestly dark sky.
• The New General Catalogue object NGC 31, a spiral galaxy in the constellation Phoenix
• The Saros number of the solar eclipse series which began on -1805 January 31 and ended on -489 March 31. The duration of Saros series 31 was 1316.2 years, and it contained 74 solar eclipses.
• The Saros number of the lunar eclipse series which began on -1774 May 30 and ended on -476 July 17. The duration of Saros series 31 was 1298.1 years, and it contained 73 lunar eclipses.

The Messier objects are a set of astronomical objects catalogued by Charles Messier in his catalogue of Nebulae and Star Clusters first published in 1774. ... This image is a Galaxy Evolution Explorer observation of the large galaxy in Andromeda, Messier 31. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... For other uses, see Galaxy (disambiguation). ... This article is about the star grouping. ... Andromeda (IPA: ) is a constellation named for the princess Andromeda (which is Greek for Ruler over men), a character in Greek mythology. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... The New General Catalogue (NGC) is the most well-known catalogue of deep sky objects in amateur astronomy. ... An example of a spiral galaxy, the Pinwheel Galaxy (also known as Messier 101 or NGC 5457) A spiral galaxy is a galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Nebulae”[1] and, as... Phoenix (IPA: ) is a minor southern constellation, introduced by Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman, and popularized by Johann Bayers Uranometria in 1603. ... A Saros cycle is a period of 6585 + 1/3 days (approximately 18 years 10 days and 8 hours) which can be used to predict eclipses of the sun and the moon. ... Photo taken during the 1999 eclipse. ... is the 31st day of the year in the Gregorian calendar. ... is the 90th day of the year (91st in leap years) in the Gregorian calendar. ... Time lapse movie of the 3 March 2007 lunar eclipse A lunar eclipse occurs whenever the Moon passes through some portion of the Earth’s shadow. ... is the 150th day of the year (151st in leap years) in the Gregorian calendar. ... is the 198th day of the year (199th in leap years) in the Gregorian calendar. ...

In sports

• The shirt number of Bayern Munich midfielder Bastian Schweinsteiger
• The jersey number of basketball great and retired Indiana Pacer Reggie Miller
• The jersey number of famed NHL goaltender Curtis "CuJo" Joseph, who currently plays for the Phoenix Coyotes
• Is the jersey number of Baseball Hall of Famer Ferguson Jenkins and Greg Maddux
• Is the retired jersey number of Baseball Hall of Famer Dave Winfield
• The jersey number of Hall of Fame NHL Goaltender Grant Fuhr
• the jersey number of Phoenix Suns forward Shawn Marion
• The jersey number for Cleveland Browns Running Back Jamal Lewis
• The car number of NASCAR driver Jeff Burton
• The jersey number of San Diego Chargers' defensive back Antonio Cromartie.
• The jersey number of Dallas Cowboys safety Roy Williams.

Reginald Wayne Miller (born August 24, 1965, in Riverside, California) is a retired American professional basketball player. ... NHL can also be an abbreviation for National Historic Landmark or Non-Hodgkins lymphoma. ... The Phoenix Coyotes are a professional ice hockey team based in the Phoenix suburb of Glendale. ... Ferguson Arthur Fergie Jenkins (born December 13, 1943 in Chatham, Ontario, Canada) was a professional baseball player. ... Gregory Alan Maddux (born April 14, 1966) is a pitcher for the San Diego Padres. ... David Mark Winfield (born October 3, 1951, in St. ... NHL can also be an abbreviation for National Historic Landmark or Non-Hodgkins lymphoma. ... Grant S. Fuhr (born September 28, 1962), is a former goaltender in the National Hockey League. ... The Phoenix Suns are a professional basketball team, based in Phoenix, Arizona. ... Shawn Dwayne Marion (born May 7, 1978 in Waukegan, Illinois) is an American professional basketball player currently for the Miami Heat of the NBA. He is widely regarded as one of the most versatile players in the league. ... Browns redirects here. ... Jeff Burton (99), Elliott Sadler (38), Ricky Rudd (21), Dale Jarrett (88), Sterling Marlin (40), Jimmie Johnson (48), and Casey Mears (41) practice for the 2004 Daytona 500 The National Association for Stock Car Auto Racing (NASCAR) is the largest sanctioning body of motorsports in the United States. ... Jeffrey Brian Burton (born June 29, 1967 in South Boston, Virginia) also sometimes referred to as JB is a NASCAR Nextel Cup Series driver. ... City Irving, Texas Other nicknames Americas Team, The Boys, The Pokes Team colors White, Silver, Silver-Green, Royal Blue, Navy Blue Head Coach Wade Phillips Owner Jerry Jones General manager Jerry Jones League/Conference affiliations National Football League (1960–present) Western Conference (1960) Eastern Conference (1961-1969) Capitol Division... For others of the same name, see Roy Williams. ...

In other fields

Thirty-one is also:

• The number of days in the months January, March, May, July, August, October and December
• The code for international direct-dial phone calls to the Netherlands
• A type of card game (see Thirty-one (game))^[1]
• A type of game played on a backgammon board
• The number of flavors of Baskin Robbins ice cream and the shops are called 31 Ice Cream in Japan
• In Star Trek, the name of Section 31, a secret police shadow organization of the Federation
• ISO 31 is the ISO's standard for quantities and units
• In the title of the anime Ulysses 31
• In the title of Nick Hornby's book 31 Songs
• Turkish slang for masturbation ("otuzbir")
• A women's honorary at The University of Alabama (XXXI)

For the game on The Price Is Right, see Card Game (pricing game). ... Thirty-one (also known as Thirty-one Knock, Big Tonka, Blitz or Scat) is a card game played by two to seven people. ... Backgammon is a board game for two players in which pieces are moved according to the roll of dice. ... Baskin-Robbins is a global chain of ice cream parlors founded by Burt Baskin and Irv Robbins in 1945 in Glendale, California. ... Missing image Ice cream is often served on a stick Boxes of ice cream are often found in stores in a display freezer. ... This article is about the entire Star Trek franchise. ... Section 31 is the unofficial designation of a rogue and officially nonexistent intelligence and defense organization resembling secret police or a black-ops organization in the Star Trek fictional universe. ... International Standard ISO 31 (Quantities and units, International Organization for Standardization, 1992) is the most widely respected style guide for the use of units of measurement, and formulas involving them, in scientific and educational documents worldwide. ... “ISO” redirects here. ... Ulysses 31 (Japanese: , French: ) is a Franco-Japanese anime series (1981) which updates the Greek and Roman mythology of Odysseus (known as Ulysses in Roman Mythology and Ulysse in French, hence the name) to the 31st century. ... 31 Songs (published in the United States as Songbook) is a 2003 collection of essays by English writer Nick Hornby about songs and (more often) the particular emotional resonance they carry for him. ... Woman masturbating, 1913 drawing by Gustav Klimt. ...

Historical years

31 A.D., 31 B.C., 1931, 2031, etc. Events Aelius Sejanus named co-Consul to the Emperor Tiberius Naevius Sutorius Macro becomes the leader of the Praetorian Guard after Sejanus is executed. ... Centuries: 2nd century BC - 1st century BC - 1st century Decades: 80s BC 70s BC 60s BC 50s BC 40s BC - 30s BC - 20s BC 10s BC 0s 10s 20s Years: 36 BC 35 BC 34 BC 33 BC 32 BC 31 BC 30 BC 29 BC 28 BC 27 BC... Year 1931 (MCMXXXI) was a common year starting on Thursday (link will display full 1931 calendar) of the Gregorian calendar. ... 2031 (MMXXXI) will be a common year starting on Wednesday of the Gregorian Calendar. ...

References

• Prime Curios! 31 from the Prime Pages