The missing value in the following figure is ____________

 

12-8 =4
Divisors of 12  are 1,2,3,4,6,12 (6)
Dovisors of 8 are 1,2,4,8,  (4)
Product = $6\times 4=24$ 
7-4=3
Divisors of  7   are 1,2    (2)
Dovisors of 4   are 1,2, 4,  (3)
Product = $2\times 3=6$

2-1=1
Divisors of   2  are 1,2,  (2)
Dovisors of  1 are 1   (1)
Product = $2\times 1=2$ 
5-3 =2
Divisors of  5    are 1, 5  (2)
Dovisors of  3 are 1 ,3   (2)
Product=4 

$=2^4=16$