Radius = 21/2 = 10.5 cm.

Volume of the sphere = \(\frac{4}{3}\pi r^3 = \frac{4}{3} \times \frac{22}{7} \times 10.5^3 = \frac{4}{3} \times \frac{22}{7} \times 1157.625 = 4851\) cm³

Each cube has volume 1 cm³, so the number of cubes = 4851.

Answer: (A) 4851