2001:0DB8:AC10:FE01:0000:0000:0000:0020
Network Prefix
Subnet ID
Interface ID
128 Bits, Expressed in Hex (Hexadecimal) with 3 parts
So 16 blocks of addresses can be handed out to different organizations
12
281 Trillion
Everyone
gets 16 blocks of addresses to sub divide their networks
65,536 subnets
And, whether you need them or not you get 16 Hex worth of address to use on network hosts in your network
18,446,744,073,709,552,000
281,474,976,710,656
Trillion
Quadrillion
Quintillion