Prime Number Calculator

Enter a whole number to check whether it's a prime number.

How It Works

A number is prime if it's greater than 1 and has no divisors other than 1 and itself. The calculator checks divisibility up to the square root of the number.

Example

17 is prime; 18 is not, since it's divisible by 2, 3, 6 and 9.

Frequently Asked Questions

Is 1 a prime number?
No, by definition prime numbers must be greater than 1.