79 (number)

Seventy-nine is the natural number following 78 and preceding 80.

79 may represent:

In mathematics

An odd number
The smallest number that can't be represented as a sum of fewer than 19 fourth powers
A strictly non-palindromic number
The 22nd prime number (the next is 83)
The smallest prime number p for which the real quadratic field Q[√p] has class number greater than 1 (namely 3)^[1]
A cousin prime with 83
An emirp, because the reverse of 79, 97, is also a prime
A fortunate prime
A prime number that is also a Gaussian prime (since it is of the form $4n %2B 3$ )
A happy prime
A Higgs prime
A Kynea prime ( $(2n %2B 1)^2-2$ )
A lucky prime
A permutable prime, with ninety-seven
A Pillai prime, because 23! + 1 is divisible by 79, but 79 is not one more than a multiple of 23
A regular prime
A prime in a residue classes 4n+3, 8n+7, and 10n+9
A right-truncatable prime, because when the last digit (9) is removed, the remaining number (7) is still prime
A sexy prime (with 73)
The n value of the Wagstaff prime 201487636602438195784363

Messier object 79 (M79), a magnitude 8.5 globular cluster in the constellation Lepus
New General Catalogue object 79 (NGC 79), a galaxy in the constellation Andromeda
Saros series 79, which began on -434 May 21 and ended on 828 June 16, lasting 1262.1 years, and with 71 lunar eclipses
Saros series 79, which began on -150 February 16 and ended on 1166 April 12, lasting 1316.2 years, and with 74 lunar eclipses

Live Seventy Nine, an album by Hawkwind
The years 79 AD (or CE), 79 BC(E), or 1979
The designation of Interstate 79, a freeway that runs from West Virginia to Pennsylvania.
The number of Star Trek: The Original Series episodes (not counting the first pilot, "The Cage", which was enclosed into "The Menagerie")
The number of recommendations in the Iraq Study Group Report
The record cumulative weeks at #1 on the Billboard charts, held by Elvis Presley
The age of Asa Long (1904-99) when she became the oldest United States checkers champion (1984)
The cost in pence of one song from the UK iTunes Store
The number of the French department Deux-Sèvres

^ H. Cohen, A Course in Computational Algebraic Number Theory, GTM 138, Springer Verlag (1993), Appendix B2, p.507. The table lists fields by discriminant, which is 4p for Q[√p] when p is congruent to 3 modulo 4, as is the case for 79, so the entry appears at discriminant 316.