What the maximum number of txout in a transaction? I know the maximum transaction size is 500Kb. 

I also know there is a maximum for sigop in a transaction (20,000?).

What I'm interested in is what is the maximum number of txouts you could include in a single transaction.
There is no practical maximum number of outputs in a transaction. The number of transactions can be up to 264-1, or 18446744073709551615. The transaction fee would be more than the total bitcoins to ever exist.