The least perfect square, which is divisible by each of 21, 36 and 66 is:

Answer: Option C

LCM of (21, 36, 66)
= 21 × 12 × 11
= 7 × 3 × 4 × 3 × 11
= 7 × 3 × 2 × 2 × 3 × 11
For perfect square multiply by 7 × 11
So that pairs of number from perfect square
$$\therefore \underset{}{\underbracket{7\times 7}}\times \underset{}{\underbracket{3\times 3}}\times \underset{}{\underbracket{2\times 2}}\times \underset{}{\underbracket{11\times 11}}$$
Required result is (which is perfect square) ⇒ 213444