Is 18 a Prime Number?
Is 18 prime?
No
18 = 2 × 3² (divisible by 2).
Why
18 is composite because it is divisible by 2 (18 = 2 × 3²), so it has factors other than 1 and itself.
A prime number is a whole number greater than 1 whose only factors are 1 and itself. To check 18, test whether any prime up to √18 divides it evenly — if none do, it is prime.
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The prime factorization calculator tests any number and shows its prime factors and all divisors.
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Frequently asked questions
Is 18 a prime number?+
No, 18 is composite because it is divisible by 2 (18 = 2 × 3²), so it has factors other than 1 and itself.
What is 18 divisible by?+
18 is divisible by more than just 1 and itself. Its prime factorization is 18 = 2 × 3².