Prime Number Checker
Test whether any number is prime and list all primes up to N.
How to use
- Enter any positive integer in the "Number to check" field.
- Click Check to instantly see whether the number is prime or composite. If composite, the smallest factor is shown.
- Optionally enter a limit and click List primes to see all prime numbers up to that value.
Related math tools
- Prime Factorization — break any integer into its prime factors
- GCD & LCM Calculator — greatest common divisor and least common multiple
- Permutation & Combination — count arrangements and selections
Frequently Asked Questions
- Is this prime checker free?
- Yes, completely free with no signup and no usage limits.
- Does my data leave my device?
- No. The primality test runs entirely in your browser using JavaScript.
- Does it work on mobile?
- Yes. Works in Safari on iPhone and Chrome on Android without any app install.
Last updated: By jarvisbox