They aren't circles, they are p-gons. A factorization is drawn as a tree where each level has p radially symmetric branches, corresponding to a prime factor p.

They aren't circles, they are p-gons. A factorization is drawn as a tree where each level has p radially symmetric branches, corresponding to a prime factor p. (Only the leafs are drawn, but you can fill in the branches and node). A prime number has only one level