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

Here, for an electron and a proton

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

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

$\therefore \frac{\left|F_e\right|}{\left|F_g\right|}=\frac{1}{4\pi {\epsilon }_0}\frac{e^2}{G{m}_{e}m}=\frac{9\times {10}^9\times {\left(1.6\times {10}^{-19}\right)}^2}{6.67\times {10}^{-11}\times 9\times {10}^{-31}\times 1.66\times {10}^{-27}}=2.4\times {10}^{39}$