Let
n be a positive integer and
S
n
a particular set of prime divisors of
n. We establish the average order of
f(n) where
f(n) stands for the cardinality of
S
n
. The
k-ary,
k-free, semi-
k-ary prime factors of
n are some of the classes of prime divisors studied in this paper.
1991 Mathematics Subject Classification 11A25 - 11A41
Key words Prime divisors - arithmetic functions - asymptotic results on primes