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Prime Number Checker

Enter a number to check if it is prime using a fast trial-division test. Runs in your browser with no sign-up required. Keeps your data private on-device.

How to use this tool

  1. Enter an integer to test primality.
  2. Review prime/composite status, nearest neighboring primes, and small divisors.
  3. Copy or export the result summary for learning or engineering workflows.

Common uses

  • Quickly screen numbers in algorithm and cryptography exercises.
  • Generate classroom examples of composite values and factors.
  • Explore prime gaps by checking sequential integer ranges.

Limits and behavior

  • This implementation targets practical small-to-mid integer checks.
  • Inputs are treated as integers for deterministic trial-division analysis.
  • Only small divisor previews are shown to keep the interface responsive.

FAQ

Does it support very large cryptographic integers?
Not for production-scale cryptography. Very large primes require big-integer arithmetic and probabilistic tests.
Why are not all divisors listed?
The tool emphasizes quick diagnosis and shows a bounded divisor preview rather than exhaustive factorization.
How are negative numbers handled?
Negative values are not prime by definition; primes are positive integers greater than 1.

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