The long-route to finding factors of numbers is to break it down into a tree.

Given 26, think of number that multiply to give you 26.

2*13=26. It's easier to put it into a tree-format.

26

/ \

2 * 13

...and don't forget the number 1! Anything multiplied by 1 is itself, and 1 will be a factor of ALL numbers. Don't forget the number itself, either. So the factors of 26 are 1, 2, 13, and 26.

To give another example that demonstrates this a little better, think of the number 32!

32

/ \

2 * 16

/ / \

2 * 2 * 8

| / / \

2 *2 * 2 * 4

| / / / \

2*2*2 * 2 * 2

So the different numbers you get are 1, 2, 4, 8, 16, and the original number 32.