No, 399 is not a prime number. It is a composite number: its digits add up to 21, which is divisible by 3, so 399 is divisible by 3.
399 has divisors other than 1 and itself. The smallest is 3: 399 ÷ 3 = 133.
Prime factorization: 399 = 3 × 7 × 19.
| Number | Prime? |
|---|---|
| 395 | No, 5 × 79 |
| 396 | No, 2 × 2 × 3 × 3 × 11 |
| 397 | Yes |
| 398 | No, 2 × 199 |
| 400 | No, 2 × 2 × 2 × 2 × 5 × 5 |
| 401 | Yes |
| 402 | No, 2 × 3 × 67 |
| 403 | No, 13 × 31 |
Another number? Use the prime number checker for any value, or see the list of prime numbers.