Abstract. The prime graph (G) of a group G is a graph with vertex
set (G), the set of primes dividing the order of G, and two distinct
vertices p and q are adjacent by an edge written p q if there is an
element in G of order pq. Let (G) = fp1; p2; :::; pkg. For p 2 (G),
set deg(p) := jfq 2 (G)jp qgj, which is called the degree of p. We
also set D(G) := (deg(p1); deg(p2); :::; deg(pk)), where p1 < p2 < :::