Go to google calculator and then put 170! and you will get 7.257416e^(306). then put 171! and you will get infinity. As a astrophysicist I do issues with this :D
That is a pretty common overflow. 171! overflows a 32 bit float.
I am not an astrophysicist, but I suggest that you, as an astrophysicist, use a mathematics engine that is a bit more robust. Might I suggest Wolfram Alpha: