Prime Number Checker

Free Prime Number Checker

Quickly determine whether a number is prime, list its prime factorisation, and find the next prime number after it. Works on integers up to several billion.

Common Uses

• Verify homework answers in number theory
• Pick small primes for hash table sizes
• Find safe modulus values for hobby crypto
• Demonstrate prime factorisation in class
• Explore prime gaps and patterns

How It Works

Primality is tested with trial division by 2 and odd numbers up to the square root of the input. The same loop is reused to extract prime factors. The next-prime finder simply increments until primality holds.

Privacy

All math runs in your browser. The number is never sent to a server.

Related: Scientific Calculator, GCD & LCM Calculator, Random Number Generator.

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