# Prime Factorisation Check whether a number is prime and break it into its prime factors — with divisor count and sum — computed with big-integer precision in your browser. ### How it works The number is divided by 2, then by each odd number in turn, up to its square root — every divisor found is a prime factor, and its multiplicity is counted. Whatever remains above 1 is itself a prime. All arithmetic uses JavaScript `BigInt`, so precision never breaks. The divisor count is the product of each exponent plus one; the divisor sum uses the geometric-series formula. Very large numbers whose smallest prime factor is huge may exceed a quick search — you’ll be told if so. --- *Source: [ocxly.com/prime-factorization.html](https://ocxly.com/prime-factorization.html) — OCXLY, free 100% client-side privacy-first tools. Free prime factorization calculator. Check if a number is prime and break it into prime factors, with divisor count and sum, using big-integer precision, entirely in your browser.*