What is the Prime Number Checker?
Check whether a number is prime and see its factors.
Enter whole number and the Prime Number Checker returns result, factors and prime factorisation. Results update as you type, and nothing you enter leaves your device.
How it is calculated
A prime number has exactly two factors: 1 and itself. The check divides by every whole number up to √n
How to use it
- Enter whole number.
- Read result in the results panel. It updates as you type.
- Change any value to compare scenarios, or use Share to send the result as a link.
Worked example
Common questions
What formula does the Prime Number Checker use?
It uses: A prime number has exactly two factors: 1 and itself. The check divides by every whole number up to √n.
What do I need to use the Prime Number Checker?
You need whole number. Sensible starting values are filled in so you can see how it works straight away.
Is the Prime Number Checker free, and is my data stored?
It is free with no sign-up. The calculation runs in your browser, so the values you enter are not sent to or stored on our server.