e-Divisor

 is called an -divisor (or exponential divisor) of a number  with prime factorization

if  and

where  for . For example, the -divisors of 36 are , , , and .

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.