91 (ninety-one) is the natural number following 90 and preceding 92. In mathematics, a natural number can mean either an element of the set {1, 2, 3, ...} (i. ... 90 (ninety) is the natural number preceded by 89 and followed by 91. ... 92 is the natural number following 91 and preceding 93. ...

← 90 91 92 93 94 95 96 97 98 99 → 89 (eighty-nine) is the natural number following 88 and preceding 90. ... 90 (ninety) is the natural number preceded by 89 and followed by 91. ... 92 is the natural number following 91 and preceding 93. ... 93 is the natural number following 92 and preceding 94. ... 94 (ninety-four) is the natural number following 93 and preceding 95. ... 95 is the natural number following 94 and preceding 96. ... 96 is the natural number following 95 and preceding 97. ... 97 is the natural number following 96 and preceding 98. ... 98 is the natural number following 97 and preceding 99. ... NOTE: A little-known fact about the number 99 is that it comes after 98, and before 100. // Ninety-nine is the ninth repdigit, a palindromic number and a Kaprekar number. ... 100 (one hundred) (the Roman numeral is C for centum) is the natural number following 99 and preceding 101. ... List of numbers — Integers This is a list of articles about numbers (not about numerals). ... The integers are commonly denoted by the above symbol. ... 0 10 20 30 40 50 60 70 80 90 → 0 (zero) is both a number and a numerical digit used to represent that number in numerals. ... 10 (ten) is an even natural number following 9 and preceding 11. ... 20 (twenty) is the natural number following 19 and preceding 21. ... 30 (thirty) is the natural number following 29 and preceding 31. ... 40 (forty) is the natural number following 39 and preceding 41. ... 50 (fifty) is the number following 49 and preceding 51. ... 60 (sixty) is the natural number following 59 and preceding 61. ... Look up seventy in Wiktionary, the free dictionary. ... 80 (eighty) is the natural number following 79 and preceding 81. ... 90 (ninety) is the natural number preceded by 89 and followed by 91. ... 100 (one hundred) (the Roman numeral is C for centum) is the natural number following 99 and preceding 101. ...
Cardinal	91 ninety-one
Ordinal	91st ninety-first
Factorization
Divisors	1, 7, 13, 91
Roman numeral	XCI
Binary	1011011
Hexadecimal	5B

Look up ninety-one in
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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. ... Commonly, ordinal numbers, or ordinals for short, are numbers used to denote the position in an ordered sequence: first, second, third, fourth, etc. ... In mathematics, factorization or factoring is the decomposition of an object (for example, a number, a polynomial, or a matrix) into a product of other objects, or factors, which when multiplied together give the original. ... 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 150 languages. ...

In mathematics

Ninety-one is a triangular number and a hexagonal number, one of the few such numbers to also be a centered hexagonal number, and it is also a centered nonagonal number and a centered cube number. It is the sum of the squares of the first six integers. A triangular number (so called because it can be arranged into a triangle) is the sum of the n natural numbers from 1 to n. ... A hexagonal number is a figurate number that represents a hexagon. ... A centered hexagonal number, or hex number is a centered figurate number that represents a hexagon with a dot in the center and all other dots surrounding the center dot in successive hexagonal layers. ... A centered nonagonal number is a centered figurate number that represents a nonagon with a dot in the center and all other dots surrounding the center dot in successive nonagonal layers. ... A centered cube number is a centered figurate number that represents a cube. ... The integers are commonly denoted by the above symbol. ...

It is the smallest positive integer expressible as a sum of two cubes in two different ways if negative roots are allowed: 91 = 6³+(-5)³ = 4³+3³. (See 1729 for more details). 1729 Cardinal One thousand seven hundred [and] twenty-nine Ordinal 1729th Factorization Divisors 7, 13, 19, 91, 133, 247 Roman numeral MDCCXXIX Binary 11011000001 Octal 3301 Duodecimal 1001 Hexadecimal 6C1 1729 is known as the Hardy-Ramanujan number, after a famous anecdote of the British mathematician G. H. Hardy regarding...

It is also the smallest pseudoprime satisfying the congruence 3ⁿ = 3 mod n.^[1] A pseudoprime is a probable prime (an integer which shares a property common to all prime numbers) which is not actually prime. ...

91 is a repdigit in base 9 (111). In recreational mathematics, a repdigit is a natural number composed of repeated instances of the same digit, most often in the decimal numeral system. ...

In science

• The atomic number of protactinium, an actinide.
• McCarthy 91 function, a recursive function in discrete mathematics

In astronomy, It has been suggested that List of elements by atomic number be merged into this article or section. ... General Name, Symbol, Number protactinium, Pa, 91 Chemical series actinides Group, Period, Block n/a, 7, f Appearance bright, silvery metallic luster Standard atomic weight 231. ... In discrete mathematics, the McCarthy 91 function is a recursive function which returns 91 for all positive integer arguments n ≤ 101 and returns for n > 101. ... Discrete mathematics, also called finite mathematics, is the study of mathematical structures that are fundamentally discrete, in the sense of not supporting or requiring the notion of continuity. ... A giant Hubble mosaic of the Crab Nebula, a supernova remnant Astronomy is the science of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earths atmosphere (such as auroras and cosmic background radiation). ...

Messier object M91, a magnitude 11.5 spiral galaxy in the constellation Coma Berenices

The New General Catalogue object NGC 91, a single star in the constellation Andromeda

The Saros number of the solar eclipse series which began on August 6, 159 BC and ended on 1175 October 16. The duration of Saros series 91 was 1334.2 years, and it contained 75 solar eclipses.

The Saros number of the lunar eclipse series which began on 161 May 26 and ended on 1459 July 15. The duration of Saros series 91 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. ... Spiral Galaxy M91. ... 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. ... An example of a spiral galaxy, the Pinwheel Galaxy (also known as Messier 101 or NGC 5457) A spiral galaxy is a type of galaxy in the Hubble sequence which is characterized by the following physical properties: A considerable total angular momentum Composed of a central bulge surrounded by a... This article or section does not adequately cite its references or sources. ... Coma Berenices (IPA: , Latin: ) is a traditional asterism that has since become a constellation. ... The New General Catalogue (NGC) is the most well-known catalogue of deep sky objects in amateur astronomy. ... STAR is an acronym for: Organizations Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... Andromeda (IPA: ) is a constellation named for the princess Andromeda (which is Greek for Ruler over men), a character in Greek mythology. ... 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. ... August 6 is the 218th day of the year in the Gregorian calendar (219th in leap years), with 147 days remaining. ... Centuries: 3rd century BC - 2nd century BC - 1st century BC Decades: 200s BC 190s BC 180s BC 170s BC 160s BC - 150s BC - 140s BC 130s BC 120s BC 110s BC 100s BC Years: 164 BC 163 BC 162 BC 161 BC 160 BC - 159 BC - 158 BC 157 BC... Events Ruaidri Ua Conchobair (Rory OConner), last High King of Ireland, submits to Henry II as vassal of Ireland with the Treaty of Windsor Ly Cao Ton becomes ruler of Vietnam William of Tyre becomes archbishop of Tyre Massacre of Abergavenny ends with several noblemen dead at the hands... October 16 is the 289th day of the year (290th in leap years). ... Time lapse movie of the 3 March 2007 lunar eclipse A lunar eclipse occurs whenever the Moon passes through some portion of the Earths shadow. ... Events March 7 - Roman emperor Antoninus Pius dies and is succeeded by co-Emperors Marcus Aurelius and Lucius Verus. ... May 26 is the 146th day of the year in the Gregorian calendar (147th in leap years). ... Events September 23 - Battle of Blore Heath. ... July 15 is the 196th day of the year (197th in leap years) in the Gregorian calendar. ...

In other fields

Ninety-one is also:

• The designation of American Interstate 91, a freeway that runs from Connecticut to Vermont.
• The code for international direct dial phone calls to India.
• In cents of a U.S. dollar, the amount of money one has if one has one each of the coins of denominations less than a dollar (penny, nickel, dime, quarter and half dollar).
• The ISBN Group Identifier for books published in Sweden.
• The year AD 91, 91 BC, or 1991.
• The jersey number worn by Dennis Rodman with the Chicago Bulls and Sergei Fedorov of the Detroit Red Wings.

Interstate 91 (abbreviated I-91) is an interstate highway in the New England section of the United States. ... It has been suggested that this article be split into multiple articles. ... Capital Montpelier Largest city Burlington Area  Ranked {{{AreaRank}}}  - Total {{{TotalAreaUS}}} sq mi ({{{TotalArea}}} km²)  - Width 80 miles (130 km)  - Length 160 miles (260 km)  - % water 3. ... ISO 4217 Code USD User(s) the United States, the British Indian Ocean Territory,[1] the British Virgin Islands, Cambodia, East Timor, Ecuador, El Salvador, Maldives the Marshall Islands, Micronesia, Palau, Panama, Turks and Caicos Islands, and the insular areas of the United States Inflation 2. ... The International Standard Book Number, or ISBN (sometimes pronounced is-ben), is a unique[1] identifier for books, intended to be used commercially. ... Pliny the Younger was named a tribunus plebis. ... Centuries: 2nd century BC - 1st century BC - 1st century Decades: 140s BC 130s BC 120s BC 110s BC 100s BC - 90s BC - 80s BC 70s BC 60s BC 50s BC 40s BC Years: 96 BC 95 BC 94 BC 93 BC 92 BC - 91 BC - 90 BC 89 BC 88... 1991 (MCMXCI) was a common year starting on Tuesday of the Gregorian calendar. ... Dennis Keith Rodman (born May 13, 1961, in Trenton, New Jersey) is an American former professional basketball player best known for his defensive and rebounding ability, leading the National Basketball Association in rebounds per game for a record seven consecutive years and earning NBA All-Defensive First Team honors seven... This article or section does not cite any references or sources. ... Sergei Viktorovich Fedorov (Russian:Сергей Викторович Фёдоров, Sergej Viktorovič Fëdorov; born December 13, 1969 in Pskov, Soviet Union; now Russia) is a professional ice hockey forward who plays for the Columbus Blue Jackets in the National Hockey League. ... The Detroit Red Wings are a professional ice hockey team based in Detroit, Michigan. ...

References

1. ^ Friedman, Erich. What's Special About This Number?