What Is the Divisibility Rule for 7?

The divisibility rule for 7 dictates that a number is divisible by 7 if subtracting 2 times the digit in the one's column from the rest of the number, now excluding the one's column digit, yields a number that is divisible by 7 or 0. Divisibility rules are simple rules that can be used to quickly determine if a number is divisible by a smaller number without a calculator.