Yes, 127 is a prime number. Its only factors are 1 and 127.
A number is prime if no smaller prime up to its square root divides it. The square root of 127 is about 11.27, 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 | 1 | No |
| 11 | 6 | No |
None of them divides 127 evenly, so 127 is prime.
| Number | Prime? |
|---|---|
| 123 | No, 3 × 41 |
| 124 | No, 2 × 2 × 31 |
| 125 | No, 5 × 5 × 5 |
| 126 | No, 2 × 3 × 3 × 7 |
| 128 | No, 2 × 2 × 2 × 2 × 2 × 2 × 2 |
| 129 | No, 3 × 43 |
| 130 | No, 2 × 5 × 13 |
| 131 | Yes |
More about 127: factors of 127 · 127 squared · square root of 127 · 127 in binary · 127 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.