College Physics (7th Edition)

S.I unit of Coulomb force constant k= S.I unit of $\frac{1}{4\pi\varepsilon_{0}}=$ S.I unit of $\frac{1}{\varepsilon_{0}}$ (as there is no unit for $\frac{1}{4\pi}$). Obviously, S.I unit of $\frac{1}{\varepsilon_{0}}$ is the inverse of the S.I unit of $\varepsilon_{0}$.