A different format for writing ip addresses
And it is a regular ip address, just written differently :)
https://www.lookip.net/ip/172.217.23.110
Funny I wasn't aware of this despite 25 years of being an Internet user
You're not alone… I been using the Internet longer'n that and I didn't ever think of converting an IP address to a decimal number either. It makes perfect sense now that it's been pointed out, but for some reason it just never crossed my mind to even try it.
The "special" case is supporting network addresses to be written as 10.2932832 ("convenient" for class A's), 172.16.61031 (ditto for B's), or just one big address like 39282329, when we're used to 4 octets separated by dots.
Not every bit of host software supports these cases anymore, as basically their sole remaining use case is as a curiosity or to circumvent bad security controls.