Following standard notations, we use $K_n$ to denote a complete graph with n vertices. We know that $K_1,K_2,K_3,K_4$ are planar graphs and a natural notion of vertex, edge, and face can be visualized easily. However, for all $n>4$, $K_n$ is not planar. So my question is: for arbitrary values of $n$, can we analytically find the minimal genus $g$ for which an embedding of $K_n$ on a two dimensional surface exists? If so, is there a systematic way to construct the minimal embedding? How many minimal embeddings are there?
P.S. I did some searches on google but did not find any satisfactory results. So I feel like I might be missing some trivial observation that prevents the existence of such embeddings. If so, please help me out!