Prime number checker
Check if a number is prime and see its prime factors.
Free prime number checker
Check whether a number is prime — that is, divisible only by 1 and itself. Enter any whole number and the tool tells you if it is prime, and if not, shows its prime factorisation. Useful for maths homework, cryptography basics and number theory.
FAQ
Is 1 prime? No, a prime must have exactly two distinct divisors; 1 has only one. What is the smallest prime? 2, the only even prime.