Dzongkha numerals

Dzongkha, the national language of Bhutan, has two numeral systems, one vigesimal, and a modern decimal system. The vigesimal system remains in robust use. Ten is an auxiliary base: the -teens are formed with ten and the numerals 1–9. Ex. cu_ci

Vigesimal

*When it appears on its own, ‘ten’ is usually said bcu tham ‘a full ten’. In combinations it is simply bcu.
Multiples of 20 are formed from khal. Intermediate multiples of ten are formed with phyed 'half to':

30			khal phyed gnyis
40			khal gnyis
50			khal phyed gsum
100			khal lnga
200			khal bcu tham
300			khal bco lnga

400 ' is the next unit: ' 400, ' 800, etc. Higher powers are 8000 ' and 160,000.

Decimal

The decimal system is the same up to 19. Then decades, however, are formed as unit–ten, as in Chinese, and the hundreds similarly. 20 is reported to be ', the same as vigesimal numeral 400; this may be lexical interference for the expected. Several of the decades have an epenthetic ', perhaps by analogy with 18 and 19, where the presumably reflects a historical 'ten':