finding a router’s IP address – multiple routers in network

I have a small network (15 computers) with a server and 3 routers which are used as access points and switches but do not assign IP addresses (only the server does that). I have assigned each of them an internal IP address, e.g. 192.168.2.31 for one of them, but I can’t remember the IP address of another and I need to log on to the admin console – is there a way to find the device on the network? I realize I can just reset the router and start over, but I don’t want to.