The cardinal and ordinal numbers. 

Cardinals are straightforward numbers, like "one, two, three..."  Ordinals are the equivalent of English "first, second, third..." and then onwards normally adding "-th" to the cardinal. Cardinals are indeclinable, including "en", unlike the same word meaning "a(n)", which is declinable. 

Ordinals decline like ordinary adjectives, but there are a few irregularities. See the section on the irregular declension of adjectives.

For details of other constructions with numbers, go to  Atlantean numerals 2