Prime Number Checker

Check whether a number is prime instantly (up to 24 digits), see its smallest factor and the nearest primes.

Enter values

Result

Is it prime?

Yes — 97 is prime

Check whether a number is prime instantly (up to 24 digits), see its smallest factor and the nearest primes.

Also known as: is it prime, prime checker, prime number calculator, is prime, prime test.

Enter whole number.
The result updates instantly as you type — press Calculate (or Enter) at any time.
Review the breakdown shown under the main result.
Use Copy result or Share to save the answer or send a link with your inputs.

A prime has exactly two divisors: 1 and itself

Using the values pre-filled in the calculator above:

the calculator returns:

No. A prime must have exactly two distinct divisors; 1 has only one.

It uses the deterministic Miller–Rabin test with fixed bases, which is proven correct for all numbers below 3.3 × 10²⁴.