Yes, 997 is a prime number. Its only factors are 1 and 997.
A number is prime if no smaller prime up to its square root divides it. The square root of 997 is about 31.58, so it is enough to test the primes 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 and 31.
| Divide by | Remainder | Divides evenly? |
|---|---|---|
| 2 | 1 | No |
| 3 | 1 | No |
| 5 | 2 | No |
| 7 | 3 | No |
| 11 | 7 | No |
| 13 | 9 | No |
| 17 | 11 | No |
| 19 | 9 | No |
| 23 | 8 | No |
| 29 | 11 | No |
| 31 | 5 | No |
None of them divides 997 evenly, so 997 is prime.
| Number | Prime? |
|---|---|
| 919 | Yes |
| 949 | No, 13 × 73 |
| 971 | Yes |
| 991 | Yes |
| 1,000 | No, 2 × 2 × 2 × 5 × 5 × 5 |
| 1,001 | No, 7 × 11 × 13 |
| 1,009 | Yes |
| 1,024 | No, 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 |
Another number? Use the prime number checker for any value, or see the list of prime numbers.