, a quasiperfect number
is a theoretical natural number n
for which the sum of all its divisors
(the divisor function σ
)) 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.