On Composite Moduli from the Viewpoint of Idempotent Numbers
  The purpose of this paper is to introduce basic concepts that are fundamental in the examination of composite moduli, while avoiding the notoriously difficult problem of prime-factorization. We introduce a new class of numbers, called idempotent numbers, that is unavoidable when researching composite moduli. Among many interesting results, we give generalizations of well-known theorems and definitions, such as the Euler-Fermat Theorem and the concept of primitive roots. We consider the generalization of the equivalence condition for the solvability of a binomial congruence to be the main result of our paper. 
J\'ozsef Vass
math.RA