As gisuck said, only 1-11 are allowed in north america (under most conditions). Any regular router, or even commercial router, sold for/in north america, should only have 1-11 (If you do have one or seen one that has more, it was likely sold outside of north america)
A good program, if you think you are experiencing wireless issues from other wireless access points, is inSSIDer. This program will scan all the area, and and show any access points it can pick up in range. it has multiple graphs/displays to show overlap etc.