How to Test if a Number is Evenly Divisible by 7
Learn how to tell whether a number is evenly divisible by seven.
Jason Marshall, PhD
To check if a number is evenly divisible by 7, start by taking the last digit of the number you’re testing and doubling it. Then subtract this number from the rest of the digits in the original number. If the resulting number is either 0 or a number that’s evenly divisible by 7, then the original number is also evenly divisible by 7． For example, is the number 126 evenly divisible by 7? Well, the final digit of 126 is 6, and double that is 2×6=12. If we subtract 12 from the rest of the digits of the original number (that is, the 12 of 126), we get 12–12=0. Since the resulting number is 0, we know that 126 must be evenly divisible by 7． In fact, as you can check: 126/7=18.
For more, see How to Tell If a Number is Divisible by 7, 8, or 9
Seven image courtesy of Shutterstock
About the Author
Jason Marshall is the author of The Math Dude’s Quick and Dirty Guide to Algebra. He provides clear explanations of math terms and principles, and his simple tricks for solving basic algebra problems will have even the most math-phobic person looking forward to working out whatever math problem comes their way.