How large a number can I check?

Any integer that fits in JavaScript's safe integer range works reliably.

Why is the range limited to 10,000 values?

It keeps the calculation fast and responsive in the browser.

What is GCD used for?

The greatest common divisor is useful for simplifying fractions and ratios.

Is my data uploaded to a server?

No. This tool runs entirely in your browser using standard web APIs, so your input never leaves your device and nothing is logged or stored on our servers.

Does it work offline and on mobile?

Yes. Once the page has loaded it keeps working without a network connection, and the layout is responsive so it stays usable on phones and tablets.

Prime Checker

Check primality, factorize numbers, list primes, and compute GCD/LCM.

Support

Works Offline

Privacy First

No Login

No API

Prime & Number Theory

Check primality, factorize, list primes, or compute GCD/LCM

Number

Result

Updates live

Is prime?

Yes

Prime factors

GCD

LCM

240

Primes in range

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

About the Prime Checker

Test whether a number is prime, break it down into its prime factors, list all primes within a range, and compute the greatest common divisor and least common multiple of two numbers.

Examples

Factorize 60

Output

2 × 2 × 3 × 5

Keyboard shortcuts

Copy the main outputCtrl / ⌘ + Shift + C
Download the resultCtrl / ⌘ + S
Share this toolCtrl / ⌘ + Shift + S
Reset the inputsAlt + R
Open the tool search paletteCtrl / ⌘ + K

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Frequently asked questions

Version 1.0.0 · Updated 2026-08-06 · Runs entirely in your browser