Divisibility

Question 0

An integer is divisible by 3 if…

Answer 0

… the sum of its digits is divisible by 3.

Example: 2,145 is divisible by 3 because 2+1+4+5 = 12 and 12 is divisible by 3.

Question 1

An integer is divisible by 2 if…

Answer 1

… its units digit is divisible by 2.

Example: 598,447,896 is divisible by 2 because 6 is divisible by 2.

Question 2

An integer is divisible by 4 if…

Answer 2

… its last two digits form a number that’s divisible by 4.

Example: 712 is divisible by 4 because 12 is divisible by 4.

Question 3

An integer is divisible by 5 if…

Answer 3

… its units digit is either 0 or 5.

Question 4

An integer is divisible by 6 if…

Answer 4

… it is divisible by both 2 and 3.

Example: 4,290 is divisible by 6 because it is divisible by 2 (it’s even) and by 3 (4+2+9+0 = 15, which is divisible by 3).

Question 5

An integer is divisible by 8 if…

Answer 5

… its last three digits form a number that’s divisible by 8.

Example: 11,640 is divisible by 8 because 640 is divisible by 8.

Question 6

An integer is divisible by 9 if…

Answer 6

… the sum of its digits is divisible by 9.

Example: 1,881 is divisible by 9 because 1+8+8+1 = 18, which is divisible by 9.

Question 7

An integer is divisible by 10 if…

Answer 7

… its units digit is 0.