  Within the framework of nonrelativistic quark-antiquark Cornell potential
model formalism, we study the annihilation of heavy quarkonia. We determine
their annihilation widths resulting into digluon, dilepton, $3\gamma$, $3g$ and
$\gamma gg$ and compare our findings with the available theoretical results and
experimental data. We also provide the charge radii and absolute square of
radial Schr\"odinger wave function at zero quark-antiquark separation for heavy
quarkonia and $B_c$ mesons.
