[simunaga]

what's AS number? how can I find out what a AS number for a domain or ip address is?

[coderholic]

You can use https://ipinfo.io - either search at https://ipinfo.io/countries/us, or use the API (note the org field):

    $ curl ipinfo.io/`dig +short facebook.com | head -n1`
    {
      "ip": "69.171.230.68",
      "hostname": "edge-star-mini-shv-17-prn1.facebook.com",
      "city": "Menlo Park",
      "region": "California",
     "country": "US",
      "loc": "37.4590,-122.1781",
      "org": "AS32934 Facebook, Inc.",
      "postal": "94025"
    }

See https://ipinfo.io/developers for more details

[simunaga]

ipinfo.io retrieves this information from somewhere. can I and how obtain this information myself, from the very source?

[jlgaddis]

https://en.wikipedia.org/wiki/Autonomous_system_(Internet)

[simunaga]

maybe you know.

can I and how obtain this information myself, from the very source, for a given domain name or company or whatever it is?

[Symbiote]

http://lmgtfy.com/?q=AS+number

etc.