  We consider \s black hole (BH) embedded in a Dehnen-$(1,4,0)$ type dark
matter halo (DDM) with two additional parameters - core radius $r_s$ and core
density $\rho_s$ apart from mass $M$. We analyze the event horizon, photon
orbits, and ISCO around DDM BHs and emphasize the impact of DDM parameters on
them. Our study reveals the adverse effect of dark matter (DM) on the radii of
photon orbits, the innermost stable circular orbit (ISCO), and the event
horizon. We find the expressions for specific energy and angular momentum for
massive particles in time-like geodesics around DDM BH and investigate their
dependence on DDM parameters. We display BH shadows for various values of core
density and radius that reveal smaller shadows cast by a \s BH surrounded by
DDM (SDDM) than a \s BH in vacuum (SV). We then move on to study quasinormal
modes (QNMs) with the help of the $6th$ order WKB method, the greybody factor
using the semi-analytic bounds method, and the Hawking spectrum for scalar and
electromagnetic perturbations. Core density and radius are found to have a
significant impact on QNMs. Since QNMs for scalar and electromagnetic
perturbations differ significantly, we can differentiate the two based on QNM
observation. The greybody factor and the power emitted as Hawking radiation are
adversely impacted by the presence of DM. We then study the weak gravitational
lensing using the Gauss-Bonnet theorem and obtain a deflection angle with
higher-order correction terms. Here, we see the deflection angle gets
attenuated due to DM. Finally, we use bounds on the deviation from \s,
$\delta$, reported by EHT for $M87^*$, Keck, and VLTI observatories for $Sgr
A^*$ to gauge the viability of our model. Our model is found to be concordant
with observations for finite parameter space. This leads to the possibility of
our galactic center being surrounded by DDM.
