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Prime Number Checker - Is It Prime?

Free prime number checker. Test if any number is prime, find its factors, and discover next/previous prime numbers.

Test if a number is prime

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Prime Number Checker

Check if any number is prime. A prime number has exactly two factors: 1 and itself.

Prime: divisible only by 1 and itself

2 is the only even prime. To check primality, test divisibility up to √n. First 10 primes: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.

Is 1 a prime number?

No. By definition, primes have exactly 2 factors. 1 has only one factor (itself), so it's neither prime nor composite.

Why are primes important?

Primes are the building blocks of numbers. Cryptography (RSA) relies on the difficulty of factoring large primes.

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Calculate factorials

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