# What is a prime number?

Kira Dobrovolskaya
January 21, 2013

Mathematics is a difficult science, but useful! Often schoolchildren have many questions related to it. For example, what a prime number is, not everyone knows. Therefore, we now tell about it.

A prime number is a natural number that can be divided without a remainder only into two divisors: by one and by itself. The unit is not a prime number. In contrast to prime numbers, compound numbers can be called. If prime numbers are divisible only by one and by themselves, then other divisors also have composite numbers.

In addition, there are mutually simple numbers. What are mutually simple numbers? These are numbers that have only one common divisor - ± 1. If numbers have other common divisors, then they are no longer mutually simple.

So, we have dealt with the theory, now we will give a few examples for a better understanding of the issue.

1. Prime numbers (divisible only by 1 and by themselves): 3, 5, 7, 11, 13, 17, 19, 23, 29.
2. Mutually simple numbers (common divisor - only +1 or -1): 2 and 11; 3 and 7; 5 and 33; 9 and 40.
3. Compound numbers (have other dividers, except 1 and themselves): 9, 10, 12, 14, 16, 18, 20, 22.