The divisibility properties of Dirichlet L-functions in infinite families of characters have been studied by Iwasawa, Ferrero and Washington. The families considered by them are obtained by twisting an arbitrary Dirichlet character with all characters of p-power conductor for some prime p. One has to distinguish divisibility by p (the case considered by Iwasawa and FerreroWashington [FeW]) and by a prime = p (considered by Washington [W1], [W2]). Ferrero and Washington proved the vanishing of the Iwasawa µ-invariant of any branch of the Kubota-Leopoldt p-adic L-function. .
