Divisibility Rule of 721

The divisibility rule for 721 is a method by which we can find out if a number is divisible by 721 or not without using the division method.

Check whether 1442 is divisible by 721 with the divisibility rule.

Step 1: Multiply the last digit of the number by 2, here in 1442, 2 is the last digit. Multiply it by 2. 2 × 2 = 4

Step 2: Subtract the result from Step 1 from the remaining values but do not include the last digit. i.e., 144–4 = 140.

Step 3: As it is shown that 140 is not a multiple of 721, therefore, the number is not divisible by 721. If the result from step 2 is a multiple of 721, then the number is divisible by 721.

Learning the divisibility rule will help kids to master division. Let’s learn a few tips and tricks for the divisibility rule of 721.

• Know the multiples of 721: Memorize the multiples of 721 (721, 1442, 2163, 2884, etc.) to quickly check the divisibility. If the result from the subtraction is a multiple of 721, then the number is divisible by 721.
   
• Use the negative numbers: If the result we get after the subtraction is negative, we will avoid the symbol and consider it as positive for checking the divisibility of a number.
   
• Repeat the process for large numbers: Students should keep repeating the divisibility process until they reach a small number that is divisible by 721. For example: Check if 4326 is divisible by 721 using the divisibility test. Multiply the last digit by 2, i.e., 6 × 2 = 12. Subtract the remaining digits excluding the last digit by 12, 432–12 = 420. Still, 420 is not a multiple of 721, so 4326 is not divisible by 721.
   
• Use the division method to verify: Students can use the division method as a way to verify and crosscheck their results. This will help them to verify and also learn.

• Divisibility Rule: The set of rules used to find out whether a number is divisible by another number or not. For example, a number is divisible by 721 if the process described in the rule results in a multiple of 721.
   
• Multiples: Multiples are the results we get after multiplying a number by an integer. For example: multiples of 721 are 721, 1442, 2163, etc.
   
• Integers: Integers are the numbers that include all the whole numbers, negative numbers, and zero.
   
• Subtraction: Subtraction is a process of finding out the difference between two numbers, by reducing one number from another.
   
• Verification: Using the division method to confirm whether the result obtained from the divisibility rule is correct or not.