Perfect numbers: Difference between revisions

{{task|Discrete math}}Write a function which says whether a number is perfect.

[[wp:Perfect_numbers|A perfect number]] is a positive integer that is

the sum of its proper positive divisors excluding the number itself.

Equivalently, a perfect number is a number that is half the sum

of all of its positive divisors (including itself).

Note: The faster [[Lucas-Lehmer test]] is used to find primes of the form 2^''n''-1, all ''known'' perfect numbers can be derived from these primes

using the formula (2^''n'' - 1) × 2^{''n'' - 1}.

It is not known if there are any odd perfect numbers (any that exist are larger than 10²⁰⁰⁰).

'''See also'''

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