  For a permutation group $G$ acting on a set $V$, a subset $I$ of $G$ is said
to be an intersecting set if for every pair of elements $g,h\in I$ there exists
$v \in V$ such that $g(v) = h(v)$. The intersection density $\rho(G)$ of a
transitive permutation group $G$ is the maximum value of the quotient
$|I|/|G_v|$ where $G_v$ is a stabilizer of a point $v\in V$ and $I$ runs over
all intersecting sets in $G$. If $G_v$ is the largest intersecting set in $G$
then $G$ is said to have the Erd\H{o}s-Ko-Rado (EKR)-property, and moreover,
$G$ has the strict-EKR-property if every intersecting set of maximum size in
$G$ is a coset of a point stabilizer. Intersecting sets in $G$ coincide with
independent sets in the so-called derangement graph $\Gamma_G$, defined as the
Cayley graph on $G$ with connection set consisting of all derangements, that
is, fixed-point free elements of $G$. In this paper a conjecture regarding the
existence of transitive permutation groups whose derangement graphs are
complete multipartite graphs, posed by Meagher, Razafimahatratra and Spiga in
[J.Combin. Theory Ser. A 180 (2021), 105390], is proved. The proof uses direct
product of groups. Questions regarding maximum intersecting sets in direct and
wreath products of groups and the (strict)-EKR-property of these group products
are also investigated. In addition, some errors appearing in the literature on
this topic are corrected.
