There is no Greatest Common Factor (GCF) for a single number. The Greatest Common Factor (GCF) is the largest factor common to two or more given numbers.
The greatest common factor (GCF) is often also called the greatest common divisor (GCD) or highest common factor (HCF). Keep in mind that these different terms all refer to the same thing: the...
There is neither a greatest common factor nor common factors of a single number, such as 21, because there cannot be any form of common factor without two or more numbers to compare. Common factors...