find the variance of first five prime numbers?

http://www.mathsisfun.com/data/standard-deviation.html

The first five primes are 2,3,5,7 and 11

2,3,5,7,11 are the first five prime numbers

Σx = 2+3+5+7+11= 28
Σx^2 = 2^2 + 3^2 + 5^2 + 7^2 + 11^2 = 208

n= 5 (number of observations)

Variance = (∑x^2 - ( ∑ x)^2 / n ) / (n-1)
= ( 208 - (28)^2 / 5 ) / 4
= 12.8