A number for which the Product of Divisors is equal to . The first few are 1, 6, 8, 10, 14, 15, 21, 22, ... (Sloane's A007422).
See also Perfect Number
Sloane, N. J. A. Sequence
in ``An On-Line Version of the Encyclopedia of Integer Sequences.''
http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.
The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.