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Prime Number Checker

Check if a number is prime

First N Prime Numbers

How Primality is Tested

  1. Numbers less than 2 are not prime
  2. 2 is the only even prime number
  3. Any other even number is not prime
  4. For odd numbers, test divisibility by all odd integers up to √n
  5. If no divisor is found, the number is prime

This trial division algorithm is efficient for numbers up to ~10 million.

First 20 Prime Numbers

235711131719232931374143475359616771

FAQ

What makes a number prime?

A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. For example, 2, 3, 5, 7, 11 are prime. The number 1 is not considered prime.

What is prime factorization?

Prime factorization is expressing a number as a product of prime numbers. For example, 60 = 2² × 3 × 5. Every integer greater than 1 has a unique prime factorization.