8.8.8.8, the network.

An autonomous system is a network with one routing policy: an internet provider, a cloud, a university, a large company. Networks swap routes with each other by AS number over BGP. IANA hands blocks of numbers to the five regional registries, which assign them to networks. The first numbers had 16 bits, up to 65,535; four-byte numbers now run past four billion.

• A prefix is an address block the network tells the rest of the internet it carries, written as an address and a length: 104.16.0.0/13 covers 524,288 addresses.
• Hivex reads them from RIPEstat, which counts a prefix when at least 10 of RIPE's route collector peers saw it in the last day. A prefix seen by fewer is left out, which hides some purely local announcements.
• A network that holds a number but announces nothing is assigned but not routing traffic: kept for later, or used only inside a private network.

64512 to 65534 and 4200000000 to 4294967294 are kept for private use inside a company's own network and never appear on the internet. AS23456 is the stand-in older routers see in place of a four-byte number. You can also type an IP address or a domain: the tool finds the network that announces it.