  We use the Horizon Run 5 cosmological simulation to study the effect of
galaxy intrinsic properties and the local environment on AGNs characterized by
their threshold of the accretion rate. We select galaxies in the stellar mass
range $10^{9.5} \le M^{}{*}/M^{}{\odot} \le 10^{10.5}$ in the snapshot at
redshift $z$=0.625. Among various intrinsic properties, we find that the star
formation rate of the host galaxy is most correlated to the AGN activity. To
quantify the environment, we use background galaxy number density (large-scale
environment) and distance and morphological type of the nearest neighbors
(small-scale environment), and study their relative effects on the AGN
properties. We find that, compared to the background density, the nearest
neighbor environment is the dominant quantity determining the bolometric
luminosity, star formation rate, and kinematic properties of AGNs and better
dictates the gas mass of the host galaxy. We show that the cold gas content in
the host galaxies is crucial in triggering AGN activity. However, when the
nearest neighbor environment effects start to act at the neighbor distance of
less than about half the virial radius of the neighbor, the neighbor
environmental effects are the most dominant factor for quasar activity.
