No, 28 is not a prime number. It is a composite number: it is even, so it is divisible by 2.
28 has divisors other than 1 and itself. The smallest is 2: 28 ÷ 2 = 14.
Prime factorization: 28 = 2 × 2 × 7 = 2² × 7.
| Number | Prime? |
|---|---|
| 24 | No, 2 × 2 × 2 × 3 |
| 25 | No, 5 × 5 |
| 26 | No, 2 × 13 |
| 27 | No, 3 × 3 × 3 |
| 29 | Yes |
| 30 | No, 2 × 3 × 5 |
| 31 | Yes |
| 32 | No, 2 × 2 × 2 × 2 × 2 |
More about 28: factors of 28 · 28 squared · square root of 28 · 28 in binary · 28 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.