L-Daddy, try this.
where:
r is the size of each permutation,
n is the size of the set from which elements are permuted, and
! is the factorial operator.
For your example, n = 39 and r = 7.
So it would be 39!/(39-7)! = 39!/32!=77,519,922,478
If you can't use the numbers over again it's that mess divided by 7!
See jriera's post.