79 (number)

79 (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.
The 22nd prime number (between and )
An isolated prime without a twin prime, as 77 and 81 are composite.
The smallest prime number p for which the real quadratic field Q[] has class number greater than 1 (namely 3).
A cousin prime with 83.
An emirp in base 10, because the reverse of 79, 97, is also a prime.
A Fortunate prime.
A circular prime.
A prime number that is also a Gaussian prime (since it is of the form ).
A happy prime.
A Higgs prime.
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 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.
Similarly to how the decimal expansion of 1/89 gives Fibonacci numbers, 1/79 gives Pell numbers, that is,
A Leyland number of the second kind and Leyland prime of the second kind, using 2 & 7 ()