of the languages that natively use seximal, Ndom's numbering system is the most well documented. spoken by around a thousand people on Yos Sudarso island, Ndom is the reason this system uses "nif" for six times six.
numbers up to six have separate names.
for numbers larger than six, the ones are separated from the sixes with "abo", which means "and".
11: mer abo sas
12: mer abo thef
13: mer abo ithin
14: mer abo thonith
15: mer abo meregh
twelve is just called "mer an thef", for two sixes.
20: mer an thef
21: mer an thef abo sas
22: mer an thef abo thef
23: mer an thef abo ithin
24: mer an thef abo thonith
25: mer an thef abo meregh
thirsy is called the very good name "tondor".
31: tondor abo sas
32: tondor abo thef
33: tondor abo ithin
34: tondor abo thonith
35: tondor abo meregh
40: tondor abo mer
41: tondor abo mer abo sas
42: tondor abo mer abo thef
43: tondor abo mer abo ithin
44: tondor abo mer abo thonith
45: tondor abo mer abo meregh
50: tondor abo mer an thef
51: tondor abo mer an thef abo sas
52: tondor abo mer an thef abo thef
53: tondor abo mer an thef abo ithin
54: tondor abo mer an thef abo thonith
55: tondor abo mer an thef abo meregh
and, as has already been stated, the Ndom word for nif is "nif". interestingly, instead of "nif an thef", the word for two nif is just "nif thef".
130: nif abo tondor
200: nif thef
unfortunately, I couldn't find any source that listed out Ndom numerals far enough to show how larger multiples of nif are handled.
other natural languages that use seximal, like the Yam languages of Papua New Guinea, have well documented base root words, but how the roots connect together into numbers is unclear.