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A prime number is a whole number greater than 1 that has exactly two factors: 1 and itself. Primes are the "atoms" of arithmetic — every integer greater than 1 can be written as a unique product of primes (fundamental theorem of arithmetic).

Trin-for-trin guide

1. 1Check if the number is greater than 1
2. 2Try dividing by every integer from 2 up to √n
3. 3If none divide evenly, the number is prime
4. 4If any divide evenly, it is composite (not prime)

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