Why aren't cardinal numbers over three inflected?

1. Are most cardinal numbers Indeclinable?
2. How do you say 2000 in Latin?
3. Do Latin numbers decline?

Are most cardinal numbers Indeclinable?

In Latin, most cardinal numerals behave as indeclinable adjectives. They are usually associated with a noun that is counted, but do not change their endings to agree grammatically with that noun.

How do you say 2000 in Latin?

2000 = 1000 + 1000 = M + M = MM. Hence, 2000 in roman numbers is expressed as MM.

Do Latin numbers decline?

There are two important rules to remember in this chapter: (1)The only cardinal numbers which decline in Latin are unus, duo, tres and milia (“one, two, three and thousands”).