Calculating the solar flux

Every second, the sun provides the Earth with a radiant energy of $1.75\times 10^{17}\mathrm{J}$ (huge value!), so if we covered the top of the atmosphere with solar panels, we'd harvest a radiant power of $1.75\times 10^{17}\mathrm{W}$. Knowing that the Earth's radius is $R_T\simeq 6400\mathrm{km}$: