Divisibility Rules Flashcards
A number is divisible by 2 if…
the last digit is even (Ex. 26)
A number is divisible by 3 if…
the sum of the digits is divisible by 3 (Ex. 216)
A number is divisible by 4 if…
the last two digits form a number that is divisible by 4 (Ex. 216)
A number is divisible by 5 if…
the last digit is a 5 or a 0 (Ex. 25, 30)
A number is divisible by 6 if…
the number is divisible by both 2 and 3 (Ex. 216)
A number is divisible by 7 if…
you can take the last digit off the number, double it and subtract the doubled number from the remaining number. If the result is evenly divisible by 7 (e.g. 14, 7, 0, -7, etc.), then the number is divisible by 7. This may need to be repeated several times. (Ex. 1603, 3101)
A number is divisible by 8 if…
the last three digits form a number that is divisible by 8 (Ex. 2264)
A number is divisible by 9 if…
the sum of all the digits is divisible by 9 (Ex. 216)
A number is divisible by 10 if…
the number ends in 0 (Ex. 260, 3100)
A number is divisible by 11 if…
you take the alternating (every second) sum of digits in the number, read from left to right and then subtract all other digits. If that is divisible by 11, so is the original number. (Ex. 1364, 2728, 3729)
A number is divisible by 12 if…
the number is divisible by both 3 and 4 (Ex. 216)
