The factors of 34 are 1, 2, 17, 34, -1, -2, -17 and -34. Factors of a number can be multiplied to get the original number as an end result. For example, 2 times 17 equals 34.
Negative numbers can also be factors because when two negative numbers are multiplied, a positive number is the result.
To find the factors of a number, first list 1 and the number. Then move to 2. If it can be multiplied evenly by another number to obtain the listed number, then it is a factor. Common factors are found by looking at the factors of two different numbers.