Ninety is a number that comes after eighty-nine and before ninety-one. It is represented as 90 in numerical form and is often associated with various concepts, such as age, percentages, and degrees. In Roman numerals, ninety is written as XC. In mathematics, ninety is an even number and can be divided by 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, and 90 itself. It is also significant in geometry, as a right angle measures ninety degrees. Additionally, Ninety can refer to various cultural references, such as the Nineties decade in the 20th century.