CDXXIX

CDXXIX is the Roman numeral representation of the number 429. It is formed by combining CD (400) + XX (20) + IX (9). The use of CD for 400 reflects subtractive notation, where C placed before D signifies 500 minus 100.

In historical numbering, Roman numerals were used across the Roman Empire and continued to be employed through the Middle Ages and into later European contexts for inscriptions, monuments, and formal dating. Today, Roman numerals appear in limited settings such as clock faces, book chapter headings, event year notations, monarchs’ regnal numbers, and some legal or ceremonial inscriptions. When CDXXIX denotes a year, it would typically indicate 429 CE (Common Era) in modern usage; if used for a year BCE, it would be 429 BCE, usually accompanied by BCE or BC to specify the era.

CDXXIX has no special meaning beyond being a valid numeral in the system of Roman numerals. It serves as an example of subtractive notation in which certain smaller letters placed before larger ones reduce the value (for example, CD = 400, IX = 9). Numerals of this form can be encountered in historical documents, academic contexts, and various forms of symbolic labeling, though they are less common in everyday modern arithmetic. See also Roman numerals and subtractive notation for broader context.