โ Math
Prime Number Checker
A prime number has exactly two divisors: one and itself. Primality testing only needs trial division up to the square root, because any factor larger than that must be paired with one smaller.
How it works
Number
Number of divisors
Prime factors
Square root
Smallest factor above 1
Frequently asked questions
How do I use the Prime Number Checker?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.