SOLUTION: There is a positive two-digit integer that is divisible by the sum of its digits AND that has exactly 5 factors. What is the sum of its factors?

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Question 491972: There is a positive two-digit integer that is divisible by the sum of its digits AND that has exactly 5 factors. What is the sum of its factors?
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
For any integer the numbers

A. one of its factors 

and 

B. %28that_integer%29%2F%28that_factor%29 

are two different integers except when the integer is a
perfect square and that factor is its square root.

So only perfect squares have an odd number of factors, since
its square root and %28that_perfect_square%29%2F%28its_square_root%29 are not two different
factors, but only one factor, since those are the same number. 

So it has to be a perfect square to have 5 factors.
So it has to be one of these:

16, 25, 36, 49, 64, or 81

16 is not divisible by 1+6, which is 7

25 is not divisible by 2+5, which is 7

36 IS divisible by 3+6, which is 9.  However 36 has 
       9 factors 1,2,3,4,6,9,12,18, and 36, and that's too many.

64 is not divisible by 6+4, which is 10.

81 is divisible by 8+1, which is 9.  It's factors are 1,3,9,27, and 81.
       And that's 5, so the number is 81.

Answer: The sum of the factors is 1+3+9+27+81 = 121

Edwin