What is the divisibility rule for 21?
The divisibility rule is explained in a short video.You could use this rule to find out if the number is divisible by 21.The rule states that you should subtract the result from the remaining number and continue until you get a single digit.The number is divided by 21 if the result is zero.The original number can be divided by 3 and 7.
Subtract the last digit from the rest of the numbers.As necessary, apply this rule over and over again.
Take the last digit and subtract it from the rest of the numbers.