Number reference
256 explained.
256: two hundred fifty-six, composite, power of two; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- two hundred fifty-six
- Classification
- composite
- Factors
- 1, 2, 4, 8, 16, 32, 64, 128, 256
- Prime factorization
- 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2
- Square root
- 16
- Cube root
- 6.349604
- Binary
- 100000000
- Octal
- 400
- Hexadecimal
- 100
- Roman numeral
- CCLVI
- Digit sum
- 13
- Digital root
- 4
What makes 256 notable
- Power of two. 256 = 2^8, which is why it shows up in memory sizes, image dimensions, and anything that repeatedly halves or doubles.
- Perfect square. 256 = 16², so a square of side 16 has an area of 256.
256 in everyday use
Two hundred fifty-six is two to the eighth power and the number of distinct values in a byte. It labels AES-256 encryption and the SHA-256 hash that secures most web traffic, appears in 256 MB and 256 GB memory sizes, and explains why the original Pac-Man breaks on level 256: the level counter overflows, drawing half the maze as garbage. The 256-colour displays of early PCs and the 256 grey levels of an 8-bit photograph come from the same limit.
Beyond computing, 256 is 4⁴ and 16², so it is a square, a fourth power, and an eighth power at once, one of the few numbers to be all three below a thousand. It has nine divisors, all powers of two, and its binary form is a one followed by eight zeros. It is the smallest number that is the fourth power of a composite number, and its digit sum is 13. In hexadecimal it is 100, the first three-digit value.
Nearby numbers
How to read this page
The factor list shows every way 256 splits into equal whole-number groups — 9 divisors in total. The prime factorisation is the compact form of that same information, and the base conversions restate 256 for contexts that do not use decimal.
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