The number 399 is an integer that comes after 398 and before 400. It is an odd number and can be expressed as the sum of three consecutive prime numbers: 131 + 137 + 131 = 399. In Roman numerals, 399 is represented as CCCXCIX. In terms of its mathematical properties, 399 is a composite number, meaning it has divisors other than 1 and itself. The factors of 399 include 1, 3, 133, and 399. Additionally, it can be found in various contexts, such as in mathematics, science, and even in historical dates.