Prime number checker

Client

Enter a whole number to see if it is prime—use with prime factorization when you need the full decomposition.

About Prime number checker

Test whether a whole number is prime—BigInt trial division in your browser, no upload. The interactive transform on this page runs in your browser tab—Toolcore does not need your paste for the core operation described above.

How to use this page

Paste or type in the main workspace, run the primary action from the toolbar, then copy or download the result. Use Load example when the page offers it, or URL prefill (?q= / ?qb=) so agents and tickets open the same input.

97 is prime

Nearby workflows on Toolcore

  • Prime factorization — Factor whole numbers into prime products—BigInt trial division in your browser, no upload. when units or numeric output should be checked on a related calculator.
  • GCD & LCM calculator — Greatest common divisor and least common multiple for two non-negative integers—BigInt, local only. when units or numeric output should be checked on a related calculator.
  • Math expression evaluator — Evaluate basic + − × ÷ arithmetic with parentheses in your browser—no variables. when units or numeric output should be checked on a related calculator.
  • Fibonacci sequence generator — Generate the first n Fibonacci numbers (0, 1, 1, 2, …) locally—up to 500 terms. when units or numeric output should be checked on a related calculator.

Common use cases

  • Verify primality before choosing RSA demo sizes or homework answers.
  • Quickly reject composite candidates before running factorization.

Common mistakes to avoid

  • Treating 1 as prime

    By definition, 1 is neither prime nor composite.

FAQ

How large can the input be?

BigInt arithmetic is used—very large integers work until the browser runs out of memory.

Is data uploaded?

No. The test runs entirely in your browser.

More tools

Related utilities you can open in another tab—mostly client-side.