You can find port number in /etc/services, although they may not be right if you have altered them (common practice with ssh, for example, and some services will re-use ports nominally allocated to something else).
You can't really disable a port, but you can block all traffic to it using iptables. To stop the block, you have to undo what you did to block it (remove the rule).
If you are using iptables, you might be better advised to go about it in a different way, depending on the numbers. The alternative approach is to drop everything, with the exception of the things that you know that you want to allow.