# What is the greatest common factor of 21 and 63?

So hence we may list all the factors of each number and see which are common to both sets and then select the highest one that is common.

Note: Some texts also refer to this as the greatest common divisor (gcd), and if the numbers are very big, we may use Euclid's Algorithm to find it.

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The greatest common factor (GCF) of 21 and 63 is 21.

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When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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