The Roman numeral "CCCXLV" represents the number 345. In this numeral, "CCC" stands for 300, "XL" represents 40, and "V" signifies 5. Roman numerals are a numeral system originating from ancient Rome, using combinations of letters from the Latin alphabet. In the context of mathematics, "CCCXLV" can be broken down into its components: 300 (CCC) + 40 (XL) + 5 (V) equals 345. This system is still used today in various applications, such as clock faces, book chapters, and movie titles, showcasing its enduring legacy in modern culture.