A perfect square number is an integer that is a square of another integer .
if we factorize above numbers , we get
$$441 = 21\times 21.$$
$$192 =4\times 4\times 4\times 3.$$
$$333 = 3\times 3\times 37.$$
and $$327 = 3\times 109.$$
So, only 441 is a perfect square of 21.
Option A is correct choice.
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