is called an -divisor (or Exponential Divisor) of
See also e-Perfect Number
References
Guy, R. K. ``Exponential-Perfect Numbers.'' §B17 in
Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 73, 1994.
Straus, E. G. and Subbarao, M. V. ``On Exponential Divisors.'' Duke Math. J. 41, 465-471, 1974.