128 bit address. 340,282,366,920,938,463,463,374,607,431,768,211,456 values
IPv6 addresses are normally written as eight groups of four hexadecimal digits. For example,
2001:0db8:85a3:08d3:1319:8a2e:0370:7334 is a valid IPv6 address. (wikipedia)
2.4 address per square micrometer in a area of 2*Pluto's semi-major axis squared.
667,000,000,000 per square micrometer of earth's surface