Why is the size 127 (prime) better than 128 for a hash-table?

Question

Supposing simple uniform hashing, that being, any given value is equally like to hash into any of the slots of the hash. Why is it better to use a table of size 127 and not 128?

Answer 1

Wikipedia actually has a good summary of this:

http://en.wikipedia.org/wiki/Hash_table

They point out that some hash functions are designed to operate ONLY with prime numbers. This article explains why powers of two are bad:

http://www.concentric.net/~Ttwang/tech/primehash.htm