1. x ÷
Divisibility Tests
Is divisible by 3?

2. An integer is divisible by 2 if…
. . .it ends in an even digit.
So 345,678,234,624 is divisible by 2. I can’t even say that number!

3. An integer is divisible by 3 if . . .
. . .the sum of the digits is a multiple of 3.
So 24,672,312 is divisible by 3 because equals 27 which is a multiple of 3. Wow that’s amazing!

4. An integer is divisible by 4 if . . .
. . .the number formed by the final two digits is divisible by 4.
So 976,816 is divisible by 4 because 16 is divisible by 4!

5. An integer is divisible by 5 if . . .
. . .the final digit is 0 or 5.
So 9,756,439,275,975 is divisible by 5. What a big number!

6. An integer is divisible by 6 if . . .
. . .the final digit is even and the digit sum is divisible by 3.
So 78,642 is divisible by 6 because = 27 AND it’s an even number!

7. An integer is divisible by 8 if . . .
. . .the number formed by the final 3 digits is divisible by 8.
So 458,112 is divisible by 8 because 112 is divisible by 8. That’s a bit hard to do!

8. An integer is divisible by 9 if . . .
. . .the sum of the digits is divisible by 9.
So 362,178 is divisible by 9 because = 27 which is a multiple of 9!
I’m getting the hang of this now!

9. An integer is divisible by 10 if . . .
. . .the final digit is 0.
So it’s easy to tell if a number is divisible by 10!

10. An integer is divisible by 11 if . . .
. . .the difference between the sums of alternating digits is divisible by 11.
So 72,479 is divisible by 11 because
( ) – (2 + 7) = 11 and 11 is divisible by 11.
I never knew that!