And the dotted representation is just that: both of these may bring you back to HN, and be pingable.

http://0xd1d8e6f0 http://3520653040

I made a short Go thingy to help you play around with this if you'd like: https://play.golang.com/p/Rybs_gwzLym

Yup, IPv4 addresses are 32 bit unsigned integers which makes them very convenient to work with. That‘s also what that 50.60.70.80 syntax is about: Those are just the four individual bytes that make up the 32bit integer, separated by a period.