Yes, 11 is a prime number. Its only factors are 1 and 11.
A number is prime if no smaller prime up to its square root divides it. The square root of 11 is about 3.32, so it is enough to test the primes 2 and 3.
| Divide by | Remainder | Divides evenly? |
|---|---|---|
| 2 | 1 | No |
| 3 | 2 | No |
None of them divides 11 evenly, so 11 is prime.
| Number | Prime? |
|---|---|
| 7 | Yes |
| 8 | No, 2 × 2 × 2 |
| 9 | No, 3 × 3 |
| 10 | No, 2 × 5 |
| 12 | No, 2 × 2 × 3 |
| 13 | Yes |
| 14 | No, 2 × 7 |
| 15 | No, 3 × 5 |
More about 11: factors of 11 · 11 squared · square root of 11 · 11 in binary · 11 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.