Python, 9310
Yeah, not the best, but at least it is something. As we say in crypto, never write your own hash function.
This is exactly 140 bytes long, as well.
F=lambda x,o=ord,m=map:int((int(''.join(m(lambda z:str(o(z)^o(x[-x.find(z)])^o(x[o(z)%len(x)])),x)))^(sum(m(int,m(o,x))))^o(x[-1]))%(2**24))
