What is the greatest common factor of 900?

Common factor usually means that you are comparing it to another number.

Here is an easy way to break it down for one number.

900

1 x 900 = 900

1 x 9 x 100 = 900

1 x 3 x 3 x 2 x 50 = 900 (notice that 3 x 3 = 9 and 2 x 50 = 100)

1 x 3 x 3 x 2 x 2 x 25 = 900 (now notice that 2 x 25 = 50 now all numbers are prime numbers)

The last line is all of the factors needed to make 900.