Seventy-nine is the natural number following 78 and preceding 80 .
In mathematics
79 is:
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 + 3 ).
A happy prime .
A Higgs prime .
A Kynea prime (having the form (2n + 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.
In science
In astronomy
In other fields
References
^ 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.