Prime & Factors

Prime & Factors is a free math & calculators tool that runs entirely in your browser — primality test & factorization. No upload, no account, no limits.

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How to use Prime & Factors

Open the Prime & Factors tool.
Paste or type your number into the input field.
The output updates as you type — adjust the options if you need a different format.
Copy the result, or share the URL to hand the exact input to someone else.

About Prime & Factors

Test whether a number is prime and, if not, break it into its prime factorization (e.g. 360 = 2³ × 3² × 5). It also reports the divisor count and the next and previous primes. Factoring is instant for numbers up to about 100 trillion.

What people use it for

Check whether a number is prime.
Find the prime factorization of an integer.
Locate the nearest primes above and below a value.

Frequently asked questions

How big a number can it factor?

Up to about 10^14 (100 trillion) using trial division, which stays instant in the browser.

What else does it report?

Whether it's prime, the prime factorization, the total number of divisors, and the next and previous primes.

Is it private?

Every calculation happens on this page, in your own browser. Your input is never sent to a server, never logged and never used for training — which also means the tool keeps working when you are offline.