For any integer n ≥ 1, let
d(n) = number of positive divisors of n
v(n) = number of distinct prime divisors of n
ω(n) = number of prime divisors of n counted with multiplicity
[for example : If p is prime, then d(p) = 2, v(p) = v(p2) = 1, \(ω\)(p2) = 2]
1
if n ≥ 1000 and \(\omega\)(n) > 2, then d(n) > log n
2
there exists n such that d(n) > 3\(\sqrt{n}\)
3
for every n, 2v(n) ≤ d(n) ≤ 2\(\omega\)(n)
4
if \(\omega\)(n) = \(\omega\)(m), then d(n) = d(m)