A whole number that is equal to the sum of its positive factors (except the number itself).

Example: 28 (positive factors are 1,2,4,7,14,28) is a Perfect number, because 1 + 2 + 4 + 7 + 14 = 28.

Example: 28 (positive factors are 1,2,4,7,14,28) is a Perfect number, because 1 + 2 + 4 + 7 + 14 = 28.

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