Let the radius of the sphere be \(r\) units. ∴ According to the given condition, \(\cfrac{4}{3} πr^3 = 4πr^2\) or, \(4πr^3 = 12πr^2\) or, \(r = 3\) \(\therefore\) Diameter of the sphere \(= 3 \times 2\) units. \(\therefore\) The numerical value of the sphere's diameter is 6 units.