Khmer numerals are characters used for writing numbers for several languages in Cambodia, most notably Cambodia's official language, Khmer. They date back to at least the oldest known epigraphical inscription of the Khmer numerals in 604 AD, found on a stele in Prasat Bayang, Cambodia, located not far from Angkor Borei.
Having been derived from the Hindu numerals, modern Khmer numerals also represent a decimal positional notation system. It is the script with the first extant material evidence of zero as a numerical figure, dating its use back to the seventh century, two centuries before its certain use in India. However, Old Khmer, or Angkorian Khmer, also possessed separate symbols for the numbers 10, 20, and 100. Each multiple of 20 or 100 would require an additional stroke over the character, so the number 47 was constructed using the 20 symbol with an additional upper stroke, followed by the symbol for number 7. This inconsistency with its decimal system suggests that spoken Angkorian Khmer used a vigesimal system.
Modern Khmer Numbers
The spoken names of modern Khmer numbers represent a biquinary system, with both base 5 and base 10 in use. For example, 6 (ប្រាំមួយ) is formed from 5 (ប្រាំ) plus 1 (មួយ).
It is generally assumed that the Angkorian and pre-Angkorian numbers also represented a dual base (quinquavigesimal) system, with both base 5 and base 20 in use. Unlike modern Khmer, the decimal system was highly limited, with both the numbers for ten and one hundred being borrowed from the Chinese and Sanskrit languages respectively. Angkorian Khmer also used Sanskrit numbers for recording dates, sometimes mixing them with Khmer originals, a practice which has persisted until the last century.
The numbers for twenty, forty, and four hundred may be followed by multiplying numbers, with additional digits added on at the end, so that 27 is constructed as twenty-one-seven, or 20×1+7.
Proto-Khmer is the hypothetical ancestor of the modern Khmer language bearing various reflexes of the proposed Mon-Khmer language. By comparing both modern Khmer and Angkorian Khmer numbers to those of other Eastern Mon-Khmer (or Khmero-Vietic) languages such as Pearic, Proto-Viet-Muong, Katuic, and Bahnaric; it is possible to establish the following reconstructions for Proto-Khmer.
Reminiscent of the standard 20-base Angkorian Khmer numbers, the modern Khmer language also possesses separate words used to count fruits, not unlike how English uses words such as a "dozen" for counting items such as eggs.