2, 3, 5, 7, 11, 13, 17, 19...

Where Prime Numbers mysteries are solved.

The simplest answer is that prime numbers are natural numbers that are only divisible by itself and 1. Natural numbers are all of the numbers starting at 1, and counting up (i.e. 1, 2, 3, 4, etc.). Primes must have exactly 2 divisors, meaning that 1 itself is not prime, because it only has 1 divisor, itself.

- 2 is prime, because it is divisible by 2, and 1, but no other numbers.
- 3 is also prime, because like 2, it is only divisible by 3 and 1, but no other numbers.
- 4 is not prime. It is divisible by itself and 1, but in addition, is also divisible by 2. Since it has a 3rd divisor, it is not prime.