Dzongkha numerals
Dzongkha, the national language of Bhutan, has two numeral systems, one vigesimal (base 20), 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. Vigesimal. <nowiki>*</nowiki>When it appears on its own, 'ten' is usually said ' 'a full ten'. In combinations it is simply '. Factors of 20 are formed from '. Intermediate factors of ten are formed with ' 'half to': 400 (20²) ' is the next unit: ' 400, ' 800, etc. Higher powers are 8000 (20³) ' ('a ɡreat score') and "" 160,000 (20⁴ ). 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 . (In any case, there is no ambiguity, because as 400 it is obligatorily ' 'one 400'.) Several of the decades have an epenthetic ', perhaps by analogy with 18 and 19, where the ' presumably reflects a historical 'ten':