Free Prime Number Checker Online

The Prime Number Checker instantly tells you whether any positive integer is prime — and if not, shows its complete prime factorization. Useful for number theory exercises, cryptography learning, and math coursework. Enter a number and get the result with working in seconds. Free, no account, runs in browser.

1. 1

   Enter any positive integer in the input field.

2. 2

   The result shows whether the number is prime or composite.

3. 3

   If composite, the complete prime factorization appears below the result.