IPv6 Subnet Calculator
Why not.
IPv6 Address: 2001:db8::25
Prefix Length: 64
Full Address: 2001:db8:0000:0000:0000:0000:0000:25
Address Range: 2001:db8:0:0:0:0:0:0 - 2001:db8:0:0:ffff:ffff:ffff:ffff
Addresses in Range: 18446744073709552000
Why not.
IPv6 Address: 2001:db8::25
Prefix Length: 64
Full Address: 2001:db8:0000:0000:0000:0000:0000:25
Address Range: 2001:db8:0:0:0:0:0:0 - 2001:db8:0:0:ffff:ffff:ffff:ffff
Addresses in Range: 18446744073709552000