Compound numbers are those divisible by other integers larger than 1.
For example, 6 can be decomposed in some ways, without remainder:
The number 7 is prime. I can not divide it. In the figures below, will always remain some balls — it will be never a rectangle.
In the above terminology, the “prime” of prime numbers refers to “first”. These indivisible numbers are the fundamental building blocks for the multiplication of numbers, and a great effort of Number Theory is upon prime numbers.
Greatest Common Divisor
Another important concept is the greatest common divisor of two numbers.
In pebble algebra, a common divisor of two numbers can be viewed as the same basis of the rectangle dividing the numbers.
The greatest common divisor is the maximum size of this basis.
Coprime numbers are those who have no common divisor. That is, the only way to put them on the same basis is when this is equal to 1.
The sections 4 and 9 are coprime.
This is a way to view prime and compound numbers in pebble algebra.