Esperanto
Esperanto is allegedly an international auxiliary language, so it handles numbers in a relatively simple way. good luck saying "kvar" though. numbers up to six can stay the same.
0: nul
1: unu
2: du
3: tri
4: kvar
5: kvin
10: ses
multiples of ten are formed with -dek (ten) in Esperanto, so multiples of six can be formed with -ses.
11: ses unu
12: ses du
13: ses tri
14: ses kvar
15: ses kvin
20: duses
30: trises
40: kvarses
50: kvinses
multiples of a hundred are also formed with a suffix, so it's only natural to do the same for multiples of nif.
100: nif
101: nif unu
110: nif ses
111: nif ses unu
200: dunif
300: trinif
400: kvarnif
500: kvinnif
1000: sesnif
1100: ses unu nif
the -illion series is an -iliono series in Esperanto, and the illions are treated as separate words.
1 0000: unu uneksiano
2 0000: du uneksiano
1 0000 0000: unu bieksiano