The book describes developments on some well-known problems regarding
the relationship between orders of finite groups and that of their
automorphism groups. It is broadly divided into three parts: the first
part offers an exposition of the fundamental exact sequence of Wells
that relates automorphisms, derivations and cohomology of groups, along
with some interesting applications of the sequence. The second part
offers an account of important developments on a conjecture that a
finite group has at least a prescribed number of automorphisms if the
order of the group is sufficiently large. A non-abelian group of
prime-power order is said to have divisibility property if its order
divides that of its automorphism group. The final part of the book
discusses the literature on divisibility property of groups culminating
in the existence of groups without this property. Unifying various ideas
developed over the years, this largely self-contained book includes
results that are either proved or with complete references provided. It
is aimed at researchers working in group theory, in particular, graduate
students in algebra.