Number analysis
80
80 is a composite even number that factors as 2^4 × 5.
80 is a composite even number that factors as 2^4 × 5.
The number itself
- Value
- 80
- Digits
- 2
- Digit sum
- 8
- Reversed
- 8
- Palindrome
- No
8 + 0
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 8.
Parity and primality
- Parity
- Even
- Prime
- No
- Prime factorisation
- 2^4 × 5
- Squarefree
- No
- Möbius μ(n)
- 0
- Nearest primes
- 79 ← → 83
Divisible by 2.
Composite — it factors as 2^4 × 5.
2 distinct prime factors, 5 with multiplicity.
At least one prime appears squared.
Zero, because a squared prime divides n.
A gap of 4 between them.
Divisors
- Aliquot sum
- 106
- Classification
- Abundant
1, 2, 4, 5, 8, 10, 16, 20, 40, 80
The proper divisors — everything except n itself.
Its proper divisors overshoot by 26.
How many integers from 1 to n share no factor with n.
Sums and additive structure
- Sum of two squares
- Yes
- Sum of three squares
- Yes
- Sum of four squares
- Yes
- Goldbach pair
- 7 + 73
4² + 8² = 80
Legendre's three-square theorem allows it.
Lagrange's four-square theorem: every non-negative integer is, without exception.
The smallest pair of primes summing to n. Goldbach’s conjecture says one always exists; it remains unproven.
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
- No
- Harshad number
- Yes
- Collatz trajectory
- 9 steps to 1
Summing the squares of its digits falls into the 4 → 16 → 37 → … → 4 cycle.
Divisible by its digit sum 8 — 80 ÷ 8 = 10.
Peaks at 80 along the way.
Written other ways
- Binary
- 1010000
- Octal
- 120
- Hexadecimal
- 50
- Base 36
- 28
- Roman numerals
- LXXX
- In words
- eighty
- Scientific notation
- 8.0 × 10^1
Is 80 a prime number?
Composite — it factors as 2^4 × 5.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 80 their own way.
- Greek (alphabetic)
- Πʹ
- Babylonian cuneiform
- 𒐕𒎙
- Tamil
- ௮௰
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.