Prime Number Checker
Check whether a number is prime, see its prime factors, and find the nearest primes.
- Is it prime?
- Yes, it is prime
- Previous prime
- 89
- Next prime
- 101
What is Prime Number Checker?
A prime number is a whole number greater than 1 that can only be divided evenly by 1 and itself. Numbers that can be divided by something else, such as 12, are called composite.
Primes matter in mathematics and in computer security, where large primes protect encrypted messages.
What this tool does
Tests a whole number up to 10 trillion for primality, shows its prime factors if it is composite, and finds the nearest primes on either side.
How to use it
- Enter a whole number.
- Read whether it is prime.
- If it is not, read its prime factors; the nearest primes are shown too.
Did you know?
- 2 is the only even prime number.
- There are infinitely many primes, which Euclid proved around 300 BC.