Find the sum of divisors of 544 which are perfect squares.  Choose the correct answer.
A) 32  B) 64  C) 42  D) 21  E) none of these

Rationale: "544 = 25 + 171 = ( 2 ) 0 + ( 2 ) 1 + ( 2 ) 2 + ( 2 ) 3 + ( 2 ) 4 + ( 2 ) 5 x ( 17 ) 0 + ( 17 ) 1 . here 20 = 1 = 11 a perfect square , 22 and 24 = 16 = 44 are perfect squares , hence , 1 + 4 + 16 = 21 . correct answer is : d"
Answer: D