Number analysis
79
79 is a prime number — divisible only by 1 and itself.
79 is a prime number — divisible only by 1 and itself.
The number itself
- Value
- 79
- Digits
- 2
- Digit sum
- 16
- Reversed
- 97
- Palindrome
- No
7 + 9
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 97.
Parity and primality
- Parity
- Odd
- Prime
- Yes
- Squarefree
- Yes
- Möbius μ(n)
- -1
- Nearest primes
- 73 ← → 83
Leaves remainder 1 on division by 2.
Divisible only by 1 and itself.
1 distinct prime factor, 1 with multiplicity.
No prime divides it twice.
(−1) to the power of 1 distinct prime factors.
A gap of 10 between them.
Divisors
- Aliquot sum
- 1
- Classification
- Deficient
1, 79
The proper divisors — everything except n itself.
Its proper divisors fall short by 78.
How many integers from 1 to n share no factor with n.
Sums and additive structure
- Sum of two squares
- No
- Sum of three squares
- No
- Sum of four squares
- Yes
A prime congruent to 3 mod 4 divides it an odd number of times, which rules it out.
Excluded by Legendre: it has the form 4^a(8b + 7).
Lagrange's four-square theorem: every non-negative integer is, without exception.
Shapes and sequences
- Figurate shapes
- None
Not triangular, square, pentagonal, hexagonal, cubic, Fibonacci, Lucas, Catalan, factorial or a power of two.
Digit curiosities
- Happy number
- Yes
- Harshad number
- No
- Collatz trajectory
- 35 steps to 1
Repeatedly summing the squares of its digits reaches 1.
Not divisible by its digit sum 16.
Peaks at 808 along the way.
Written other ways
- Binary
- 1001111
- Octal
- 117
- Hexadecimal
- 4F
- Base 36
- 27
- Roman numerals
- LXXIX
- In words
- seventy-nine
- Scientific notation
- 7.9 × 10^1
Is 79 a prime number?
Yes. 79 has no divisors other than 1 and itself.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 79 their own way.
- Greek (alphabetic)
- ΟΘʹ
- Babylonian cuneiform
- 𒐕𒌋𒐝
- Tamil
- ௭௰௯
References
Further reading: Wikipedia · Wikidata
Notations, naming and the links above come from Wikidata, whose structured data is dedicated to the public domain under CC0-1.0. Retrieved 2026-10-07.