The ratio of magnitude of electrostatic force and gravitational force between an electron and a proton is

For an electron and a proton : 

Electrostatic force, $\left|F_e\right|=\frac{1}{4{\mathrm{\pi \epsilon }}_0}\frac{e^2}{r^2}$

Gravitational force, $\left|F_g\right|=\frac{G{m}_e{m}_p}{r^2}$

Therefore $\frac{\left|F_e\right|}{\left|F_g\right|}=\frac{1}{4{\mathrm{\pi \epsilon }}_0}\frac{e^2}{G{m}_e{m}_p}$

        $= \frac{9\times {10}^9\times {(1.6\times {10}^{-19})}^2}{6.67\times {10}^{-11}\times 9.1\times {10}^{-31}\times 1.66\times {10}^{-27}}=2.3\times {10}^{39}$