Prime Number Checker
Check if any number is prime. List all primes in a range. Find the next prime. Shows full factorisation.
How to use the Prime Checker
What is a prime number?
A prime number is any whole number greater than 1 that has no divisors other than 1 and itself. Examples: 2, 3, 5, 7, 11, 13, 17, 19, 23. The checker also shows the complete factorisation of non-prime numbers.
List and find
List all primes in any range up to 100,000. Find next prime goes forward from any number to find the nearest prime above it. Both are useful for mathematics, cryptography, puzzles and programming challenges.
Frequently asked questions
Is the Prime Checker free to use?
Yes, the Prime Checker is completely free. There is no sign-up, no account required, and no limit on how often you can use it.
How accurate is the Prime Checker?
The Prime Checker uses standard mathematical formulas and produces results accurate to standard precision. For critical applications, always verify with an authoritative source.
What devices does the Prime Checker work on?
The Prime Checker works on any device with a modern web browser — desktop, laptop, tablet, or phone. It is mobile-friendly and works offline once the page has loaded.