Is equal, just split four and 12 in 1/2
The prime numbers are 17, 19, 23, 29, 31, and 37
Prime number - A number thats only factors are 1 and itself
The surface area formula for any sphere is 4(pi)(radius)^2
The radius is half of the diameter.
18.6 / 2 = 9.3
So, plug into the formula and solve.
4(3.14)(9.3)^2 = 1086.3 mm^2
The answer is 138 if u plain out subtract it