A number may be made by multiplying two or more other numbers together. The numbers that are multiplied together are called factors of the final number.
All numbers have a factor of one since one multiplied by any number equals that number.
All numbers can be divided by themselves to produce the number one. Therefore, we normally ignore one and the number itself as useful factors. The number fifteen can be divided into two factors which are three and five. The number twelve could be divided into two factors which are 6 and 2. Six could be divided into two further factors of 2 and 3.