# 79 (number)

| ||||
---|---|---|---|---|

Cardinal | seventy-nine | |||

Ordinal |
79th (seventy-ninth) | |||

Factorization | prime | |||

Prime | 22nd | |||

Divisors | 1, 79 | |||

Greek numeral | ΟΘ´ | |||

Roman numeral | LXXIX | |||

Binary |
1001111_{2} | |||

Ternary |
2221_{3} | |||

Quaternary |
1033_{4} | |||

Quinary |
304_{5} | |||

Senary |
211_{6} | |||

Octal |
117_{8} | |||

Duodecimal |
67_{12} | |||

Hexadecimal |
4F_{16} | |||

Vigesimal |
3J_{20} | |||

Base 36 |
27_{36} |

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

## In mathematics[edit]

**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 4
*n*+ 3). - A happy prime.
^{[5]} - A Higgs prime.
^{[6]} - A Kynea prime (having the form (2
*n*+ 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 4
*n*+ 3, 8*n*+ 7, and 10*n*+ 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[edit]

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

### In astronomy[edit]

- 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

## In other fields[edit]

- Live Seventy Nine, an album by Hawkwind
- The years 79 BC, AD 79 or 1979
- Any of several highways numbered 79
- The number of the French department Deux-Sèvres
- The number of bricks on the one dollar note pyramid
^{[citation needed]}

## References[edit]

**^**"Sloane's A016038 : Strictly non-palindromic numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**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 4*p*for**Q**[√*p*] when*p*is congruent to 3 modulo 4, as is the case for 79, so the entry appears at discriminant 316.**^**"Sloane's A006567 : Emirps".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**"Sloane's A046066 : Fortunate primes".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**"Sloane's A035497 : Happy primes".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**"Sloane's A007459 : Higgs' primes".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**"Primes of the form (2^n + 1)^2 - 2 = 4^n + 2^(n+1) - 1".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**"Sloane's A031157 : Numbers that are both lucky and prime".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**"Sloane's A063980 : Pillai primes".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.**^**"Sloane's A007703 : Regular primes".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-29.