The factors of six are one, two, three and six. Factors are the numbers that can be multiplied together to get the number being factored. Six multiplied by one equals six, and two multiplied by three equals six; no other positive integers multiplied together result in a product of six.
One is always a factor of a number, as is the number itself. For positive numbers, one is always the lowest factor, and the number itself is the highest factor. All other factors fall somewhere in between them. A number that only has itself and the number one as factors is called a prime number.