There is likely no limit on even the number of IP addresses unless it has some strange restriction.
It may not really matter.... Some of the more common things that limit a router are how many NAT entries it can have (bit torrent uses a lot) and how much cpu it has to encrypt data for wireless. I am sure it also has some limit to unique mac addresses etc etc.
The bottom line will be the router can handle more devices than your internet connection can handle. You will run out of bandwidth first. No way to say how many devices it can be. It could be 2 if they both were pulling huge amounts of data.
A larger concern would be how many wireless devices you can actually use and this does not really depend on the router. Wireless is a free for all and the devices transmit over the top of each other causing errors for all. The more active devices you have the slower it gets. Again you will run out of wireless bandwidth well before the router runs out of processing power.