Prime Number Calculator

Use this prime number calculator to verify if a number is prime or not. If the number that you entered is composite, the calculator will tell you by what factor your number is divisible.

Facts about Prime and Composite Numbers

By definition a number is prime if it is divisible only by one and itself. The only two factors of a prime number are one and the number itself.

Except for 0 and 1 (who are neither prime, nor composite), a whole number that is not prime is composite. A composite number has other factors besides one and itself. Two is the only even prime number. Any other even number is composite because it has two as a factor.

Examples

The following numbers are prime: 2, 3, 5, 7, 11, 13, 17, 19,...

The following numbers are composite: 4, 6, 8,9, 10, 12, 14, 15, 16, 18, 20

Use the above calculator to establish whether a large number is prime or composite.

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