In [1], Das et.al. considered the monogenic semi group S M with zero having {0, x, x 2 , ..., x n }. Also they defined undirected graph Γ(S M) associated with S M whose vertices are the non-zero elements x, x 2 , ..., x n and any two different vertices x i and x j are adjacent if i + j > n (for 1 ≤ i, j ≤ n). In this paper we present sigma index of corona products of any two monogenic semigroup graphs Γ(S 1 M) and Γ(S 2 M). Also we give forgotten index and irregularity index of monogenic semigroup graphs.