How many system or device can one wireless router handle.Is there any limit on number of devices??

I work in a office that has wireless and 10 computers and handheld devices run off of it. My apartment has floor level wireless and 20 apartments run off the same server. So I assume it is the available frequency of the router and your signal from your Internet Service Provider. this way you get the best signal. My other wireless router can run up to three computers and three wireless without affecting downloads and it will also get a good signal from about 75 meters away.