Yes, 23 is a prime number. Its only factors are 1 and 23.
A number is prime if no smaller prime up to its square root divides it. The square root of 23 is about 4.80, 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 23 evenly, so 23 is prime.
| Number | Prime? |
|---|---|
| 19 | Yes |
| 20 | No, 2 × 2 × 5 |
| 21 | No, 3 × 7 |
| 22 | No, 2 × 11 |
| 24 | No, 2 × 2 × 2 × 3 |
| 25 | No, 5 × 5 |
| 26 | No, 2 × 13 |
| 27 | No, 3 × 3 × 3 |
More about 23: factors of 23 · 23 squared · square root of 23 · 23 in binary · 23 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.