Home/Random Prime Number
A number with no divisors but itself and one, drawn evenly from every prime in your range. For the classroom, for a puzzle, for a test case that needs a number that will not factor.
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The primes in the range are found first, then one is drawn from that list. That matters because primes thin out as numbers grow: drawing a number and testing it would favour nothing, but would take far longer near the top of a large range.
Two is the only even prime, and it is in the list like any other — the range starts there for that reason.
These are small primes for teaching and puzzles. The primes behind real encryption are hundreds of digits long and are generated very differently; nothing here is a substitute for that.
The draw itself uses the browser’s cryptographic random source and runs entirely on your device.
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