  In this paper we study ATLAS results on underlying event in pp collisions at
$\sqrt{s}$=0.9, 7 and 13 TeV. We show that the center-of-mass energy
dependences of the charged-particle production sensitive to the underlying
event ("transverse" region) and to the hardest partonic interaction ("towards"
and "away" regions) in pp collisions can be both understood in terms of the
change of the inclusive average multiplicity. Within uncertainties, the
corresponding particle production as a function of the leading charged particle
shows no significant $\sqrt{s}$-dependence for the three regions once they are
scaled according to the relative change in multiplicity. The scaling properties
reported here are well reproduced by PYTHIA 8.212 tune Monash 2013 and suggest
an universality of the underlying event in hadronic interactions at high
$\sqrt{s}$. Based on the simulations, we observed that the same scaling
properties are also present in the average number of multi-partonic
interactions as a function of the leading charged particle. Moreover, the
multiplicity distributions associated to the underlying event exhibit a KNO
scaling.
