It's not a phone number because it doesn't need to resolve back to anything in particular. With carrier grade nat for instance, it could be shared by many people. At best it's shared by a house.

With regards of tracking you with the help of the ISP, if you have someone with those resources, it's not you storing an IP address that's their biggest concern.

Geoinformation can also change daily. Figuring it out afterwards isn't reliable.