Published online by Cambridge University Press: 20 November 2018
Let n ≥3 and m≥3 be integers. Let Kn be the cyclotomic field obtained by adjoining a primitive nth root of unity to the field of rational numbers. Let denote the maximal real subfield of Kn. Let hn (resp.,
) denote the class number of Kn (resp.,
). For fixed m we show that m divides hn and hn for asymptotically almost all n. Also for those Kn and
with a given number of ramified primes, we obtain lower bounds for certain types of densities for m dividing hn and
.