Portuguese
Portuguese has separate words for every number up to dozen three, and we can keep all of them up to a dozen.
0: zero
1: um
2: dois
3: três
4: quatro
5: cinco
10: seis
11: sete
12: oito
13: nove
14: dez
15: onze
20: doze
we can handle numbers after that the same way Portuguese handles most numbers that aren't divisible by ten, using the word "e" for addition (and using the Portuguese word for dozen for numbers up to thirsy).
21: dúzia e um
22: dúzia e dois
23: dúzia e três
24: dúzia e quatro
25: dúzia e cinco
also like in Spanish, multiples of ten usually end with -enta in Portuguese. the -ensa solution works here too.
30: trinsa
40: quarensa
50: cinquensa
the Portuguese word for ten tens is "cem", and multiples of cem are formed with variants of the -centos suffix. the seximal equivalent of this is to turn "nif" (loaned as "nife") into a -nifes suffix.
100: nife
110: nife e seis
200: dunifes
300: trenifes
400: quatronifes
500: quinnifes
1000: seis nife
1100: seis nife e nife
1200: seis nife e dunifes
finally, the -exian series can be loaned directly.
1 0000: unexião
1 0000 0000: biexião