What is the least common factor of 9 and 21?

To answer the question, "What is the least common factor of 9 and 21?", we will start by defining and listing factors of 9 and 21.

Factors of 9 are all the integers that when multiplied by another integer equal 9. Likewise, factors of 21 are all the integers that when multiplied by another integer equal 21.

The factors of 9 are 1, 3, and 9.

The factors 21 are 1, 3, 7, and 21.

When you ask, "What is the least common factor of 9 and 21?", least is the key word here. Least means smallest. Thus, the smallest or least common factor that 9 and 21 have in common is 1.

Note that all integers, such as 9 and 21, have 1 as one of its factors. Thus, the answer to the least common factor of any two integers greater than 0 will always be 1.

Now that you know the least common factor of 9 and 21, you may also be interested in knowing the greatest common factor of 9 and 21. The greatest factor 9 and 21 have in common, per the list above, is 3.

When you asked for the least common factor of 9 and 21, did you mean least common multiple? If so, the least common multiple of 9 and 21 is 63.

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