Answer
$1.1\times10^{21}$ photons.
Work Step by Step
Energy of one photon= $\frac{hc}{\lambda}$
$=\frac{(6.626\times10^{-34}\,Js)(2.99792458\times10^{8}\,m/s)}{6.5\times10^{-6}\,m}$
$=3.056\times10^{-20}\,J$
Number of photons=$ \frac{\text{Total energy}}{\text{Energy of one photon}}$
$=\frac{32.8\,J}{3.056\times10^{-20}\,J}$
$=1.1\times10^{21}$
