- Quasiperfect number
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 2"n" + 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 numbergreater than 1038 and have at least seven distinct prime factors. [cite journal|author=Hagis, Peter & Cohen, Graeme L.,|title=Some results concerning quasiperfect numbers|journal=J. Austral. Math. Soc. Ser. A|volume=33|year=1982|pages=275–286]
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