The number 
in the expression 
for a multiperfect
number is called its class.
Multiperfect Number Class
See also
Multiperfect NumberExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Multiperfect Number Class." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/MultiperfectNumberClass.html