DCLXVI is a Roman numeral that represents the number 666. In the Roman numeral system, "D" stands for 500, "C" for 100, "L" for 50, "X" for 10, and "VI" for 6. When combined, these values add up to 666, which is often associated with various cultural and religious contexts. The number 666 is famously known as the "Number of the Beast" in the Christian Bible, specifically in the Book of Revelation. It has been interpreted in various ways throughout history, often symbolizing evil or the Antichrist, leading to its frequent appearance in literature, films, and popular culture.