Find the number that is missing in the third circle.

Find the number that is missing in the third circle. Correct Answer 21

The logic followed here is:

1) We taking a square root of all outside digit.

2) Then addition of all number.

3) We get a middle number.

Pattern follow in first figure

 √36 + 64 + 25 + 49

→ 6 + 8 + 5 + 7

→ 26 

In second figure 

25 + 144 + 36 + 64

→ 5 + 12 + 6 + 8

→ 31

Similarly,

In third figure

9 + 25 + 16 + 81

→ 3 + 5 + 4 + 9

→ 21

Hence, the correct answer is "21".