The electric field at a point in a certain region of free space due...

The electric field due to a point charge $Q$ at a distance $r$ is given by $E = \dfrac{1}{4\pi\epsilon_0}\dfrac{Q}{r^2}$.

Given that the electric field $E = 0$, this implies that the distance $r \to \infty$ (assuming $Q \neq 0$).

The electric potential due to the charge $Q$ at a distance $r$ is given by $V = \dfrac{1}{4\pi\epsilon_0}\dfrac{Q}{r}$.

As $r \to \infty$, the electric potential $V \to 0$.

Therefore, the electric potential at that point is zero.

Answer: zero.