Congruence and Real Life Applications - I

Congruence is a very powerful concept in the study of Number Theory, Cryptography and Modular Arithmetic. For a given positive integer n, any two integers u1 and u2 are said to be congruent modulo n if they have the same remainder upon division by n. In this paper we discuss properties of congruence, Fermat’s theorem and Wilson's theorem. We also discuss various examples of real life applications of these concepts, especially the various divisibility tests and computations related to calendar.