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Prime Checker

Test primality and factor integers with BigInt.

Verdict
100 is composite
Value
100
Digits
3
Class
composite
Even
yes
Prime factorization (|n|)
2^2 × 5^2
Prime factors
  • 2^2
  • 5^2

Primality uses Miller–Rabin (deterministic witness sets plus extra bases). Factorization uses trial division and Pollard's Rho (Brent). Up to 36 digits (absolute value). Negatives, 0, and 1 are not prime.

关于Prime Checker

Knowing whether a number is prime — and how it factors — comes up in crypto, contests, and homework. Trial division by hand gets painful fast, and it's easy to miss a composite. This tool runs Miller–Rabin for a prime/composite verdict and trial division plus Pollard's Rho (Brent) for factorization. Separators like commas and underscores are allowed. Negatives factor |n| and are never called prime (primes are integers ≥ 2). 0 and 1 are not prime. Everything uses BigInt in your browser; nothing is sent to toco.tools servers. Very large hard semiprimes may not fully factor, but the primality check still completes.

使用方法

  1. Enter an integer (commas or underscores allowed)
  2. Read the prime / composite verdict
  3. Read the factorization (2^a × 3^b …)

常见问题

How large can numbers be?

Up to 36 digits (absolute value). Factorization is reliable through about 18 digits; harder larger semiprimes may not fully split.

Are 1 or negatives prime?

No. Primes are integers ≥ 2. For negatives, we show the factorization of |n|.

Is my input sent anywhere?

No. All calculation runs in your browser; nothing is sent to toco.tools servers.