The GCF is 3.
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The greatest common factor (GCF) for 9 and 21 is 3.
3
Oh, dude, the greatest common factor of 9, 15, and 21 is 3. It's like the superhero that swoops in to save the day, dividing all those numbers without breaking a sweat. So yeah, 3 is the chosen one in this math problem.
21 = 7 x 3 , 9 = 3 x 3 ; for the Least Common Multiple (LCM), 21 already is a multiple of 7. 21 & 9 have a common factor of 3, so LCM = 21 x 3 = 63
Since 9 is a factor of 63, all of its factors are common.