A domatic (total domatic) k-coloring of a graph G is an assignment of k colors to the vertices of G such that each vertex contains vertices of all k colors in its closed neighborhood (neighborhood). The domatic (total domatic) number of G, denoted d(G) (d t (G)), is the maximum k for which G has a domatic (total domatic) k-coloring. In this paper, we show that for two non-trivial graphs G and H, the domatic and total domatic numbers of their Cartesian product G H is bounded above by max{|V (G)|, |V (H)|} and below by max{d(G), d(H)}. Both these bounds are tight for an infinite family of graphs. Further, we show that if H is bipartite, then d t (G H) is bounded below by 2 min{d t (G), d t (H)} and d(G H) is bounded below by 2 min{d(G), d t (H)}. These bounds give easy proofs for many of the known bounds on the domatic and total domatic numbers of hypercubes [8,31] and the domination and total domination numbers of hypercubes [16,22] and also give new bounds for Hamming graphs. We also obtain the domatic (total domatic) number and domination (total domination) number of ndimensional torus n i=1 C k i with some suitable conditions to each k i , which turns out to be a generalization of a result due to Gravier [13] and give easy proof of a result due to Klavžar and Seifter [23].