Question

write all the factors of 21. use commas to separate them.

Explanation:

Step1: Recall factor definition

Factors of a number divide it evenly.

Step2: Start from 1

1 is a factor of 21 since $21\div1 = 21$.

Step3: Check 2

21 is odd, so 2 is not a factor.

Step4: Check 3

$21\div3=7$, so 3 and 7 are factors.

Step5: Check 4

$21\div4 = 5.25$, 4 is not a factor.

Step6: Check 5

$21\div5 = 4.2$, 5 is not a factor.

Step7: Check 6

$21\div6=3.5$, 6 is not a factor.

Step8: Consider the number itself

21 is a factor of 21 since $21\div21 = 1$.

Answer:

1, 3, 7, 21