Finally we have prime numbers, perhaps the “quirkiest” of all the numbers, these are the ones that only divide by themselves or 1. For example the chart below lists all of the prime numbers between 1 and 600:

NB: As shown, "2" is also a prime number, the only even prime.


However, if a number can be divided evenly it is called a composite number, being formally defined as a number which has at least one other positive divisor other than itself and one, so for example whereas the number 17 is a prime number, the number 18 is a composite number because it divides by 1, 2, 3, 6 and 9 (indeed, being next door neighbour  to a prime number but having so many divisors itself you could in fact say that the number 18 is indeed a very composite number :-)).


As I said before I don’t intend to mention any other types of number, suffice it to say that there are very many other types of number such as complex numbers, perfect numbers etc. So, what can we do with numbers? 


Well we can add them together, subtract one from the other, multiply them together or divide one by the other. 


There are of course many other operations we can square them cube them, raise them to powers, turn them into fractions, turn them into decimals, change the bases (that is change the number that the groups are based on, more on that later) and so on, and so forth.


For the first part of this section I’m going to concentrate on the 4 basic mathematical functions of addition, subtraction, multiplication and division. 


Further on into this section I will talk about bases (for example base 10, otherwise known as the decimal or denary system, base 2 which is also known as the binary system, base 16 which is hexadecimal (and a bit more complicated than some of the others)).