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Encyclopedia > 15th
(Redirected from 15th)

15 (fifteen) is the natural number following 14 and preceding 16.



<< 10 11 12 13 14 15 16 17 18 19 >>

Cardinal 15
fifteen
Ordinal 15th
fifteenth
Factorization
Divisors 1, 3, 5, 15
Roman numeral XV
Binary 1111
Hexadecimal F



In mathematics

Fifteen is a triangular number and a hexagonal number, and the 4th Bell number. Fifteen is the double factorial of 5. It is a composite number; its proper divisors being 1, 3 and 5. With only two exceptions, all prime quadruplets enclose a multiple of 15, with 15 itself being enclosed by the quadruplet (11, 13, 17, 19).


In hexadecimal, as well as all higher bases, fifteen is represented as F.


Fifteen is the magic constant of a 3 by 3 magic square:



In science

In astronomy,

Messier object M15, a magnitude 7.5 globular cluster in the constellation Pegasus
The New General Catalogue object (http://www.ngcic.org/) NGC 15, a spiral galaxy in the constellation Pegasus
The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros1-175.html) of the solar eclipse series which began on -2557 July 1 and ended on -1223 September 8. The duration of Saros series 15 was 1334.2 years, and it contained 75 solar eclipses.
The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1-175.html) of the lunar eclipse series which began on -2219 April 30 and ended on -921 June 19. The duration of Saros series 15 was 1298.1 years, and it contained 73 lunar eclipses.

In other fields

Age 15 is:

  • The age of a quinceañera, a Hispanic girl celebrating her fifteenth birthday.
  • The age for obtaining a driver's (or learner's) permit in jurisdictions where the age for a driver's license is sixteen.

Fifteen is:



  Results from FactBites:
 
The 15th Air Force (539 words)
The 15th dropped 303,842 tons of bombs on enemy targets in 12 countries of Europe, including military installations in eight capital cities.
Ploesti was protected by 150 first class fighters and 250 heavy flak guns when the 15th, with the cooperation of the RAF 205th Group of night bombers, began a series of attacks against it on April 5.
The 15th followed up the Ploesti attacks by dropping 10,000 tons of bombs in attacks on three synthetic oil plants in Silesia and one in Poland, reducing their combined production by February of 1945 to 20% of what it was in June of 1944.
1st Battalion ? 15th Infantry Regiment (1396 words)
The 15th fought in the capture of Toronto and Fort George in April and May 1813, and covered the retreat of militia troops from Fort George in December 1813.
The 15th Infantry was reactivated on 3 May 1861 with headquarters in Newport Barracks, KY. Before the end of the Civil War, the regiment fought 22 major engagements, including Chattanooga, Chickamauga, Murfreesborough, and Atlanta.
When the 15th returned to the U.S. in 1907, it was assigned to Fort Douglas, UT. In November 1911, however, the 2nd Battalion returned to Tientsin, China, as part of the international peace-keeping mission designed to protect civilians during the Chinese Revolution.
  More results at FactBites »


 
 

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