Yes, s_pugh, V is 19.
As you have P, X, Q, V, A and R, you've probably solved the clues for 9d (which gives P and X), 34a, which gives the relationship between Q and V, and 35a and 5d, which confirm V (and therefore Q) and also give A and R. You should be able to deduce J from 4d, T, Y and D from 10a and 11a, H from 31a and 4a, and B from 1a (in that order). I solved the clues in a slightly different order, but reached the same set of 12 letters. I didn't use Euclid's formula originally, but I have subsequently found that it dramatically reduces the possibilities for Q and V implied by 34a.