What is a number called if it is equal to the sum of its proper divisors (excluding itself)?
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Perfect number
The smallest perfect number is 6, because its divisors are 1, 2, and 3, and 1+2+3 = 6. The next perfect number is 28. They are quite rare and have fascinated mathematicians since antiquity.
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- What term describes a number that is the sum of all its divisors, excluding the number itself?