Algebra

Please think this problem through, it is a basic problem that shouldn't require any help. Here are some hints: 

Note that each number is 6 plus the last number. So can we manipulate the sum to be divisible by six? That way we can apply the formula $1 + 2 + ... + n = \frac{n(n-1)}{2}$? 

Sum =  [first term + last term ] * [number of terms / 2]

Nuimber of terms =   [6021 - 21 ]  / 6   +  1    =  1001

Sum =   [ 21 + 6021 ] *  [ 1001 / 2 ] =   3,024,021