No, 18 is not a prime number. It is a composite number: it is even, so it is divisible by 2.
18 has divisors other than 1 and itself. The smallest is 2: 18 ÷ 2 = 9.
Prime factorization: 18 = 2 × 3 × 3 = 2 × 3².
| Number | Prime? |
|---|---|
| 14 | No, 2 × 7 |
| 15 | No, 3 × 5 |
| 16 | No, 2 × 2 × 2 × 2 |
| 17 | Yes |
| 19 | Yes |
| 20 | No, 2 × 2 × 5 |
| 21 | No, 3 × 7 |
| 22 | No, 2 × 11 |
More about 18: factors of 18 · 18 squared · square root of 18 · 18 in binary · 18 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.