The dissertation consists of four chapters. The first chapter is an introduction, where we formulate new generalizations of Artin\u27s conjecture for primitive roots and also mention some existing formulations. In chapter two we prove the following result: given a CM elliptic curve E defined over a number field, we have an asymptotic formula counting the number of prime ideals [special characters omitted] with norm ≤ x, such that the reduction of E modulo [special characters omitted] is cyclic. In this formula the error term estimate is given with effectively computable constant. In chapter three we point out that the arguments given in Bilharz\u27s paper for an example of nonexistence of natural density don\u27t seem to be clear. We correc...