No, 256 is not a prime number. It is a composite number: it is even, so it is divisible by 2.
256 has divisors other than 1 and itself. The smallest is 2: 256 ÷ 2 = 128.
Prime factorization: 256 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 2⁸.
| Number | Prime? |
|---|---|
| 252 | No, 2 × 2 × 3 × 3 × 7 |
| 253 | No, 11 × 23 |
| 254 | No, 2 × 127 |
| 255 | No, 3 × 5 × 17 |
| 257 | Yes |
| 258 | No, 2 × 3 × 43 |
| 259 | No, 7 × 37 |
| 260 | No, 2 × 2 × 5 × 13 |
More about 256: factors of 256 · square root of 256 · 256 in binary.
Another number? Use the prime number checker for any value, or see the list of prime numbers.