However, there are some natural numbers, the one just through 1 and can share through itself. Let's take the number 7. In fact, you can only go through them 1 and share by yourself, when there should be no remainder. It can only be written as the product of two natural numbers: 7 = 1· 7 or 7:1. It's the same with numbers 11.
11 =1· 11 or 11 1.
Such numbers are called prime numbers. How is it with 13,17 and with 37? They are prime numbers. is 27 also a prime number? No, because 27 = 3 · 9. is 1 a prime number ? You can 1 share by yourself, and you can 1 by dividing, but both are the same, namely 1:1 = 1. 1 cannot be the product of two natural numbers; Therefore 1 also not a prime number.