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In mathematics, a quasiperfect number is a theoretical natural number n for which the sum of all its divisors (the divisor function σ(n)) is equal to 2n + 1. Quasiperfect numbers are abundant numbers.

No quasiperfect numbers have been found so far, but if a quasiperfect number exists, it must be an odd square number greater than 1038 and have at least seven distinct prime factors. [1]

Perfect number

References

1. ^ Hagis, Peter & Cohen, Graeme L., (1982). "Some results concerning quasiperfect numbers". J. Austral. Math. Soc. Ser. A 33: 275-286.