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Prime Number Checker
prime · number · sieve · factor · math
PRIME
17 is a prime number
Previous prime
13
Next prime
19
How to use
- 1
Enter a number in 'Check Number' to test primality.
- 2
See its factorization and the previous/next prime.
- 3
Switch to 'List Primes' to list all primes up to a limit.
FAQ
Is this tool free?
Yes — no sign-up, no installation, completely free to use right away.
What is this tool?
This tool explores numbers — checking primes, generating sequences like Fibonacci, or testing number patterns. It's handy for math homework, coding practice, or curiosity. Everything is calculated in your browser.