Prime Number Tools
Check primes, find factors, generate prime ranges
100% client-side processing
97 is a prime number
2^2 x 3 x 5
The 10th prime is 29
Check primes, find factors, generate prime ranges
100% client-side processing
97 is a prime number
2^2 x 3 x 5
The 10th prime is 29
Prime Number Tools bundles four calculators in one: test whether a number is prime, break it into prime factors, list every prime in a range, or find the nth prime. Whether you are doing homework, prepping for a math competition, or just curious if your phone number is prime, the answer is one click away.
A prime is a number divisible only by 1 and itself, and these indivisible numbers are the atoms of arithmetic. The Fundamental Theorem of Arithmetic states that every integer greater than 1 factors into primes in exactly one way — which is why breaking 91 into 7 × 13 always gives the same answer, no matter how you approach it.
Primes follow no simple pattern. Euclid proved over two thousand years ago that they never run out, and twin primes like 11 and 13 may be infinite too, though nobody has proved it yet. That unpredictability is exactly what makes them useful: RSA encryption works because multiplying two huge primes is easy, while factoring the product back apart is brutally hard. Primes even show up in nature — periodical cicadas emerge in 13- and 17-year cycles, likely to avoid syncing with predator lifecycles.
A prime number is a natural number greater than 1 that has no divisors other than 1 and itself.
No, 1 is not considered a prime number by definition.
By trial division — it only checks divisors up to the square root of the number, which keeps it fast even for large inputs.
It underpins RSA cryptography, simplifies fractions, and helps find the GCD and LCM of numbers.