Sort:  

(1+1) x (1+1) = 4
(2+2) x (2+2) = 16
(3+3) x (3+3) = 36

I will reveal the answer after few hours. Let everyone answer :D

11 x 11 = 121 -> (1+2+1) = 4
22 x 22 = 484 -> (4+8+4) = 16
33 x 33 = 1089 -> (1+0+8+9) = 18

Without ruling, there is actually many answers to it. A few I got were 32 & 36.

Thanks for participating. The answer is 36. I am upvoting to the right answer.