Prime Number Checker

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.

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.