Finding cliques in a big graph
These kind of problems are in general very hard with the decission version of a problem often being NP-hard, so I doubt you will find an algorithm fast enough, unless your graph has some peculiarity which allows you to discard a large number of vertices.

Since you restrict it to cliques of exactly 17 vertices then trivially there is an $O(n^{17})$ algorithm, but I'd hardly call this fast. To do this simply step through all subsets of 17 vertices in lexicographical order and check whether they form a clique. Note that this is exactly $\binom{n}{17}$ subsets. Note however, that for an input graph which is itself a clique, there are $\binom{n}{17}$ cliques of comprised of 17 vertices, and hence this trivial algorithm is optimal if we consider only worst case scaling, since simply reading a list of all such cliques takes $\binom{n}{17}$ steps. In order to do better than this, you need a graph with some structure.

So for your specific case of $n=8568$ you potentially have $2 \times 10^{52}$ cliques of 17 vertices. Further since you have more than 12 million edges, this is enough for a maximally connected graph of 5000 vertices, which would have approximately $2 \times 10^{48}$ unique subsets 17 vertices which form cliques, so for the parameters you have listed it is entirely possible that you simply cannot enumerate cliques fast enough to give you a reasonable run time.