A common factor of two positive whole numbers is a number that divides evenly into both of them. Their greatest common factor (sometimes abbreviated GCF) is the largest number that divides evenly into both of them. Another name that’s used for “greatest common factor” is “greatest common divisor” (sometimes abbreviated GCD).
Read MoreIt’s helpful to think about multiples and divisibility as two parts of the same idea. We know that 10 is “divisible” by 5 because when we do the division 10/5, the result 2 is a whole number. It’s the fact that the result is a whole number that proves that 10 is divisible by 5.
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