Rule 9:
To factor an integer, simply break the integer down into a group
of numbers whose product equals the original number. Factors are separated by multiplication signs. Note that the number 1 is the factor of every number. All factors of a number can be divided evenly into that number.
Problem 6: Is 7 a factor of 21? Why?
Answer. Since 21 can be written as , 7 is a factor. Also
is an even division.