Leonhard Euler is one of THE most prominent mathematicians in history. His various excursions into different fields of mathematics have spread his name far and wide in most mathematical applications. In particular, he was introduced many notations we take for granted today; these include the symbols for pi and e, f(x), sin x, cos x, and sigma notation, to name a few. It is impossible to include all of the fields of mathematics in which Euler studied on this single webpage. His impact in the mathematical world has been lasting and essential to the status of the subject area today. One of the things I find interesting about Euler was his Phi Function, which is defined by Phi(x)