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 Description  
 Perfect Number:  A number in which the sum of all of its proper divisors equals the number itself.

For example, the number 6 has proper divisors 1, 2, and 3. The sum of these proper divisors is 6, and so 6 is a perfect number.



The first three perfect numbers are
6 = 1 + 2 + 3,
28 = 1 + 2 + 4 + 7 + 14, and
496 = 1 + 2 + 4 + 8 + 16 + 31 + 62 + 124 + 248.