Let denote the set of the numbers less than and Relatively Prime to , where is the
Totient Function. Then if
See also Bauer's Identical Congruence, Totient Function
References
Hardy, G. H. and Wright, E. M. ``A Theorem of Leudesdorf.'' §8.7 in
An Introduction to the Theory of Numbers, 5th ed. Oxford, England: Clarendon Press, pp. 100-102,
1979.