Yes, 157 is a prime number. Its only factors are 1 and 157.
A number is prime if no smaller prime up to its square root divides it. The square root of 157 is about 12.53, so it is enough to test the primes 2, 3, 5, 7 and 11.
| Divide by | Remainder | Divides evenly? |
|---|---|---|
| 2 | 1 | No |
| 3 | 1 | No |
| 5 | 2 | No |
| 7 | 3 | No |
| 11 | 3 | No |
None of them divides 157 evenly, so 157 is prime.
| Number | Prime? |
|---|---|
| 153 | No, 3 × 3 × 17 |
| 154 | No, 2 × 7 × 11 |
| 155 | No, 5 × 31 |
| 156 | No, 2 × 2 × 3 × 13 |
| 158 | No, 2 × 79 |
| 159 | No, 3 × 53 |
| 160 | No, 2 × 2 × 2 × 2 × 2 × 5 |
| 161 | No, 7 × 23 |
More about 157: factors of 157 · square root of 157 · 157 in binary.
Another number? Use the prime number checker for any value, or see the list of prime numbers.