What is the greatest whole number that MUST be a factor of the sum of any six consecutive positive odd numbers?

Let the first odd number be 2n-5 (n ≥ 3), then the 6 consecutive odd numbers are:

2n-5, 2n-3, 2n-1, 2n+1, 2n+3, 2n+5

And their sum is:

2n-5 + 2n-3 + 2n-1 + 2n+1 + 2n+3 + 2n+5 = 12n

The greatest common factor for all n(≥ 3) of 12n is 12.

Thus 12 is the greatest whole number that MUST be a factor of the sum of any six consecutive positive odd numbers.