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{{Infobox number
| number = 50
| numeral = quinquagesimal
| divisor = 1, 2, 5, 10, 25, 50
| unicode = ↆ
}}
'''50''' ('''fifty''') is the [[Natural number|natural number]] following [[49 (number)|49]] and preceding [[51 (number)|51]].

==In mathematics==
[[File:square-sum-50.png|thumb|50 as the sum of two non-zero squares]]
Fifty is the smallest number that is the sum of two non-zero square numbers in two distinct ways: 50 = 1<sup>2</sup> + 7<sup>2</sup> = 5<sup>2</sup> + 5<sup>2</sup> (see image).<ref>de Koninck, J.M. (2009). ''Those fascinating numbers''. AMS Bookstore. p. 18. {{ISBN|0-8218-4807-0}}.</ref> It is also the sum of three squares, 50 = 3<sup>2</sup> + 4<sup>2</sup> + 5<sup>2</sup>, and the sum of four squares, 50 = 6<sup>2</sup> + 3<sup>2</sup> + 2<sup>2</sup> + 1<sup>2</sup>. It is a [[Harshad number]].<ref>{{Cite web|url=https://oeis.org/A005349|title=Sloane's A005349 : Niven (or Harshad) numbers|website=The On-Line Encyclopedia of Integer Sequences|publisher=OEIS Foundation|access-date=2016-05-30}}</ref>

50 is a Stirling number of the first kind: <math>\left[{5\atop 2}\right] = 50</math> and also a [[Narayana number]]: <math>\operatorname{N}(6, 3) = \operatorname{N}(6, 4) = 50</math>

There is no solution to the equation [[Euler's totient function|φ]](''x'') = 50, making 50 a [[Nontotient|nontotient]].<ref>{{Cite web|url=https://oeis.org/A005277|title=Sloane's A005277 : Nonients|website=The On-Line Encyclopedia of Integer Sequences|publisher=OEIS Foundation|access-date=2016-05-30}}</ref> Nor is there a solution to the equation ''x'' − φ(''x'') = 50, making 50 a [[Noncototient|noncototient]].<ref>{{Cite web|url=https://oeis.org/A005278|title=Sloane's A005278 : Noncotients|website=The On-Line Encyclopedia of Integer Sequences|publisher=OEIS Foundation|access-date=2016-05-30}}</ref>

Fifty is the sum of the number of faces that make up the [[Platonic solid]]s (4 + 6 + 8 + 12 + 20 = 50).


==In science==
* The [[Physics:Atomic number|atomic number]] of [[Chemistry:Tin|tin]]
* The fifth [[Physics:Magic number|magic number]] in nuclear physics

==In religion==
* In [[Unsolved:Kabbalah|Kabbalah]], there are 50 Gates of Wisdom (or Understanding) and 50 Gates of Impurity{{Citation needed|date=August 2011}}
* The traditional number of years in a [[History:Jubilee (biblical)|jubilee]] period.<ref>Leviticus 25:10</ref>
* The Christian Feast of [[Religion:Pentecost|Pentecost]] takes place on the 50th day of the Easter Season
* The Jewish [[Religion:Pentecost|Pentecost]] takes place 50 days after the Passover feast (the holiday of Shavuoth).
* In Hindu [[Philosophy:Tantra|tantric tradition]], the number 50 holds significance as the 50 Rudras in the [[Philosophy:Kashmir Shaivism|Malinīvijayottara]] correlate with the 50 [[Social:Phoneme|phoneme]]s of [[Social:Sanskrit|Sanskrit]], as well as with the 50 severed heads worn around goddess [[Religion:Kali|Kali']]s head. The [[Philosophy:Mantra|mantra]] ''Aham'' ("I am"), as laid out in the [[Philosophy:Vijñāna Bhairava Tantra|Vijñāna Bhairava]] represents the first अ(a) and last ह(ha) phonemes of the Sanskrit alphabet and is believed to represent [[Religion:Ultimate reality|ultimate reality]], in accordance with its non-dual philosophy.

==In sports==
* In cricket one day internationals, each side may bat for 50 overs.

==In other fields==
'''Fifty''' is:
* There are 50 states in the United States of America.
* The TV show ''Hawaii Five-O'' and its reimagined version, ''Hawaii Five-0'', are so called because Hawaii is the last  (50th) of the states to officially become a state.
* 5-O (Five-Oh) - Slang for police officers and/or a warning that police are approaching. Derived from the television show ''Hawaii Five-O''<ref name="Rhodes1997">{{cite book|author=Karen Rhodes|title=Booking Hawaii Five-O: An Episode Guide and Critical History of the 1968–1980 Television Detective Series|url=https://books.google.com/books?id=_FruSwC9UjwC&pg=PA265|date=1 February 1997|publisher=McFarland|isbn=978-0-7864-8666-3|page=265}}</ref>
* A calibre of ammunition (0.50&nbsp;inches: see .50 BMG)
* In millimetres, the [[Focal length|focal length]] of the normal lens in 35&nbsp;mm photography
* The [[Percentage|percentage]] (50%) equivalent to one half, so that the phrase "fifty-fifty" commonly expresses something divided equally in two; in business this is often denoted as being the ultimate in equal partnership
* In years of marriage, the gold or "golden" wedding anniversary

==Businesses==
*Fifty (outlet store) - Formerly "Fifty Outlet". Outlet stores, mostly in Spain, owned by Tendam, selling its brands e.g. Cortefiel, Springfield, and others'

==See also==
* List of highways numbered 50

==References==

{{Reflist}}


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[[Category:Integers]]

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