Answer by jose_castro_arnaud for Tweetable hash function challenge

Ruby, 9309 collisions, 107 bytes

def hash(s);require'prime';p=Prime.first(70);(0...s.size).reduce(0){|a,i|a+=p[i]**(s[i].ord)}%(2**24-1);end 

Not a good contender, but I wanted to explore a different idea from other entries.

Assign the first n primes to the first n positions of the string, then sum all prime[i] ** (ascii code of string[i]), then mod 2**24-1.