Is 18 a prime number?
No, 18 is not a prime number. It is divisible by 2: 18 = 2 × 9.
Is 18 prime?
Pick any whole number from 1 to 10,000.
How to work it out
- 1
A prime number has exactly two factors: 1 and itself.
- 2
It is enough to test the primes up to √18 ≈ 4.24. If none of them divides 18, it is prime.
- 3
2 divides 18 exactly, so it is not prime. Its prime factorisation is
LaTeX source of the formulas on this page
\[ 18 = 2 \times 3^{2} \]Testing 18 by the primes up to its square root
| Prime | Division | Result |
|---|---|---|
| 2 | 18 ÷ 2 | divides exactly (9) |
| 3 | 18 ÷ 3 | divides exactly (6) |
Questions
Is 18 a prime number?
No, 18 is not a prime number. It is divisible by 2: 18 = 2 × 9.
What is the next prime after 18?
19.
What is the prime number before 18?
17.
What are the factors of 18?
1, 2, 3, 6, 9, 18.