Let 
be the sum of the infinitary
divisors of a number 
. An infinitary 
-multiperfect number is a number 
such that 
. Cohen (1990) found 13 infinitary 3-multiperfects,
seven 4-multiperfects, and two 5-multiperfects.
Infinitary Multiperfect Number
See also
Infinitary Perfect NumberExplore with Wolfram|Alpha
References
Cohen, G. L. "On an Integer's Infinitary Divisors." Math. Comput. 54, 395-411, 1990.Guy, R. K. Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 54, 1994.Referenced on Wolfram|Alpha
Infinitary Multiperfect NumberCite this as:
Weisstein, Eric W. "Infinitary Multiperfect Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/InfinitaryMultiperfectNumber.html