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.
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