Without seeing the strings to which you refer, I can't say they are or aren't, but URLs and IPs (which are, after all, URLs - the addresses of computers) can be represented strictly as numeric strings without alpha characters, punctuation characters, or special characters - and, in some technical settings commonly are so rendered. In fact, the strings can be decimal, octal, hexadecimal, alphanumeric, or binary - whichever, the computer converts them to binary - the only "language" it really understands - before doing anything with them, coming or going - in the end, its all bits, "Ones" and "Zeros".
Given the appropriate (and quite common) software, a webmaster can determine not only the IP of a visiting computer, but the browser that computer used to access the website, certain of that browser's settings, whether the website was accessed directly (ie - the address was typed into the address bar) or via a redirect (the browser was sent to the website from another website, either by by clicking on a link or through some other action performed by the originating website), as well as info pertaining to the pages viewed, time-on-site, number of visits, that sorta thing.
For an eye-opening look at some of what your computer says about you, click
HERE