The easiest way to check it out is is simply to Google the actual number itself and see what pops up (is it an automated robot dialing to solicit, etc.).
To trace back a number and see if it is landline or cell phone and then get an idea of city/region, use fonefinder.net
If you get a result on fonefinder.net like "T-Mobile Cellular Phone Number" then, if you were so inspired, you could email the number at something like
2815551212@tmomail.net instead of texting to that number and ask who it is, what they want, etc.