Number analysis
256
256 is a composite even number that factors as 2^8.
256 is a composite even number that factors as 2^8.
The number itself
- Value
- 256
- Digits
- 3
- Digit sum
- 13
- Reversed
- 652
- Palindrome
- No
2 + 5 + 6
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 652.
Parity and primality
- Parity
- Even
- Prime
- No
- Squarefree
- No
- Prime power
- 2^8
- Powerful
- Yes
- Möbius μ(n)
- 0
- Nearest primes
- 251 ← → 257
Divisible by 2.
Composite — it factors as 2^8.
1 distinct prime factor, 8 with multiplicity.
At least one prime appears squared.
A single prime raised to a power.
Every prime factor appears at least squared.
Zero, because a squared prime divides n.
A gap of 6 between them.
Divisors
- Aliquot sum
- 255
- Classification
- Deficient
1, 2, 4, 8, 16, 32, 64, 128, 256
The proper divisors — everything except n itself.
Its proper divisors fall short by 1.
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
- 5 + 251
0² + 16² = 256
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
- Square number
- Yes — the 16th
- Power of two
- Yes — 2^8
Digit curiosities
- Happy number
- No
- Harshad number
- No
- Collatz trajectory
- 8 steps to 1
Summing the squares of its digits falls into the 4 → 16 → 37 → … → 4 cycle.
Not divisible by its digit sum 13.
Peaks at 256 along the way.
Written other ways
- Binary
- 100000000
- Octal
- 400
- Hexadecimal
- 100
- Base 36
- 74
- Roman numerals
- CCLVI
- In words
- two hundred and fifty-six
- Scientific notation
- 2.56 × 10^2
Is 256 a prime number?
Composite — it factors as 2^8.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 256 their own way.
- Morse code
- · · − − − · · · · · − · · · ·
- Devanagari
- २५६
- Tamil
- ௨௱௫௰௬
- Thai
- ๒๕๖
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.