DCLXXXIV is a Roman numeral that represents the number 684. In this numeral, "D" stands for 500, "C" for 100, "L" for 50, "X" for 10, and "V" for 5. The combination of these letters adds up to 684, following the rules of Roman numeral notation. Roman numerals are a numeral system originating from ancient Rome. They use combinations of letters from the Latin alphabet to signify values. This system was widely used throughout the Roman Empire and is still seen today in various contexts, such as clock faces and the naming of monarchs.