Prime number is one that cannot be decomposed into factors except 1 and itself (numbers 2 3 5 7 are prime.) see factoring

 

Explanation:

All natural numbers have at least two factors: one and the same. see what is a divisor

There are numbers that also have other factors

Examples:

 

      • 15 = 1·15 = 3·5 (factors of 15: 1,3,5,15)
      • 12 = 1·12 = 2·6 = 3·4 (factors of 12: 1,2,3,4,6,12)
      • 7 = 1·7 (factors of 7: 1,7)

 

In this example, the number 7 is prime because it only can be factorized by 1 and itself

 

A number is prime if there aren’t more factors than itself and unity.

Conclusions

Prime number is one that can not be obtained by the multiplication of 2 numbers. (Except the same by 1) see what is a multiple

 

Prime number is the number that can not be obtained by multiples of any number (except 1 and itself)

 

In this table we can see:

In red the multiples of 2 except 2

In blue multiples of 3 except 3

In green multiples of 5 except 5

 

and so on, with 7 (red triangle), 11 (blue triangle), 13 (green triangle) …

The numbers have remained unchecked are the prime numbers up to 30, finds that none can be decomposed into prime factors. see factoring