On nonabelian simple groups having the same prime graph as an alternating group

All instances of coincidence between the prime graphs of nonabelian simple groups $G$ and $S$ are found, where $G$ is an alternating group of degree $n\ge5$ and $S$ is a nonabelian finite simple group. The precise bound of the maximal number of pairwise nonisomorphic nonabelian simple groups with the same prime graph is given in the case that one of these groups is an alternating group.