Number reference
79 explained.
79: seventy-nine, prime; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- seventy-nine
- Classification
- prime
- Factors
- 1, 79
- Prime factorization
- 79
- Square root
- 8.888194
- Cube root
- 4.29084
- Binary
- 1001111
- Octal
- 117
- Hexadecimal
- 4F
- Roman numeral
- LXXIX
- Digit sum
- 16
- Digital root
- 7
What makes 79 notable
- Prime. 79 is prime: it has exactly two divisors, 1 and itself, so it cannot be split into equal whole-number groups any other way.
79 in everyday use
Seventy-nine is the atomic number of gold, so every gold atom has 79 protons, and the symbol Au comes from the Latin aurum. Mount Vesuvius buried Pompeii and Herculaneum in AD 79. Because gold sits between platinum (78) and mercury (80), medieval alchemists' dream of turning mercury into gold was, in a sense, a matter of removing one proton — something achieved only in particle accelerators at absurd cost.
Seventy-nine is the 22nd prime and an emirp, since 97 is also prime. It is a happy number: 49 + 81 = 130, then 1 + 9 = 10, then 1. It pairs with 83 as a cousin prime, the two differing by 4. It leaves a remainder of 3 when divided by 4, so it cannot be written as a sum of two squares. In binary it is 1001111.
Nearby numbers
How to read this page
Because 79 is prime, the factor list stops at 1 and 79 itself, so it cannot be shared into equal whole-number groups. That is also what makes it useful as a building block: every larger number with 79 in its prime factorisation inherits it from here.
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