Question 298967
Suppose a positive integer n is divisible by 21 and by 9. What is the smallest possible number of positive integers that divide n?
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21 = 3*7 and 9 = 3*3

So the smallest integer divisible by both 21 and 9 is 3*3*7 or 63,
their LCM.

63 is divisible by 1,3,7,9,21, and 63.  That's six.

Any other integer divisible by both 21 and 9 will also be 
divisible by those 6, and at least one other.

So the answer has to be 6.

Edwin</pre>