A prime number is a whole number (counting number, natural number) that is larger than 1 but only divisible by itself and 1.
Some prime numbers are 2, 3, 5, 7, 11, ..
4 is not a prime number because it is the product of 2 x 2 as well as 1 x 4.
6 is not a prime number because it is the produt of 2 x 3 as well as 1 x 6.
2 is a prime number because the only product is 1 x 2.
3 is a prime number because the only product is 1 x 3.
If the number is a prime number it can only be factored into 1 and itself.
A number is not a prime number if it can also be factored in a different way besides 1 and itself.