79 (number)

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

In mathematics

79 is:

• An odd number.
• The smallest number that can not be represented as a sum of fewer than 19 fourth powers.
• A strictly non-palindromic number.^[1]
• 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).^[2]
• A cousin prime with 83.
• An emirp, because the reverse of 79, 97, is also a prime.^[3]
• A fortunate prime.^[4]
• A prime number that is also a Gaussian prime (since it is of the form 4n + 3).
• A happy prime.^[5]
• A Higgs prime.^[6]
• A Kynea prime (having the form (2n + 1)² − 2).^[7]
• A lucky prime.^[8]
• A permutable prime, with ninety-seven.
• A Pillai prime,^[9] because 23! + 1 is divisible by 79, but 79 is not one more than a multiple of 23.
• A regular prime.^[10]
• 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.

In science

• The atomic number of the chemical element gold (Au) is 79.

In astronomy

• 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

In other fields

• Live Seventy Nine, an album by Hawkwind
• The years 79 AD (or CE), 79 BC(E), or 1979
• Any of several highways numbered 79
• The number of the French department Deux-Sèvres

References