A number which is the sum of its Unitary Divisors with the exception of itself. There are no Odd unitary perfect numbers, and it has been conjectured that there are only a Finite number of Even ones. The first few are 6, 60, 90, 87360, 146361946186458562560000, ... (Sloane's A002827).

**References**

Guy, R. K. ``Unitary Perfect Numbers.''
§B3 in *Unsolved Problems in Number Theory, 2nd ed.* New York: Springer-Verlag, pp. 53-59, 1994.

Sloane, N. J. A. Sequence
A002827/M4268
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.

Wall, C. R. ``On the Largest Odd Component of a Unitary Perfect Number.'' *Fib. Quart.* **25**, 312-316, 1987.

© 1996-9

1999-05-26