Prime Number Checker

Test integer primality and show factors for composite numbers.

Prime Number Checker
Local input
Output
Processing…
About this tool

Made for the task at hand.

Determine whether an integer is prime using a deterministic 6k±1 division check. Composite results include a useful factor pair.

How to use

  1. Enter an integer with absolute value up to ten billion.
  2. Review whether it meets the definition of a prime.
  3. For composites, inspect the smallest and complementary factors.
Your work stays yours.
Tool inputs are processed locally in your browser and are never sent to KitVerse servers. Clear the workspace when using a shared device.
Common questions
Are 1, zero, or negative numbers prime?

No. Prime numbers are integers greater than 1 with exactly two positive divisors.

Why is there an input limit?

Trial division becomes slow for very large values; the limit keeps local browser checks responsive and honest.