The factors of 66 are one, two, three, six, 11, 22, 33 and 66. Factors of a particular number are whole numbers that divide evenly into that number without a remainder. Factors are always less than or equal to the number of which they are factors.
The number one is always a factor of a whole number, as is the number itself. Some clues exist to indicate factors of various numbers with two or more digits. For example, two is always a factor of any whole number that ends in zero or an even number. Numbers ending in zero or five have five as a factor, and any number ending in zero has 10 as a factor. Knowing the factors of numbers helps in reducing fractions to lowest terms.