Prime Number Checker
Check if a number is prime and find the next prime.
How it works
A prime number has exactly two divisors: 1 and itself. The checker tests divisors up to the square root of the number. It accepts whole numbers up to one trillion.
FAQ
Is this calculator free?
Yes. No signup is needed and nothing you enter is stored.
Is the result exact?
Results are rounded for display. For financial, medical, or legal decisions, confirm with a professional.
Do my numbers leave my device?
No. The calculation runs in your browser.