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Q: The sum of 6 and a number is 21?

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16

p + 21.

Le the "number" be x. The sum is x + 6.

For this particular problem, you just need to experiment a little. 1 + 2 + 3 + 4 + 5 +6 = 21 (6 integers).

The solution (not sum) to the equation 21 = 3c + 6 is as follows:21 = 3c + 621 - 6 = 3c + 6 - 615 = 3c3c = 153c/3 = 21/3c = 7

That means the number itself is divisible by three. the sum of the digits in 144, for example, is 9. 144 divided by 3 is 48. The sum of the digits in 21 is 3. 21 divided by 3 is 7.If the number is an even number and the sum of the digits is divisible by 3, the number is also divisible by 6. 144 is even and the sum of the digits is divisible by 3, so 144 is also divisible by 6. 144/6 = 24. And finally, if the sum is divisible by 9, the number itself is also divisible by 9. 27 is an example of this.

5x + 6

the sum of my digits is 6? answer=60

a+21

First, you want to know the definition of a perfect number: A perfect number is an integer which is equal to the sum of all its positive integer divisors that are less than itself. Example: The positive integer divisors of 6, less than 6, are 1, 2, and 3. The sum of those divisors is 1 + 2 + 3 = 6. Therefore, 6 is a perfect number. Now, 21 does not meet this definition and therefore is not a perfect number. Let's try it. There are three positive divisors of 21, namely, 1, 3, and 7, that are less than 21, itself. (There are no others.) But the sum of these divisors is 1 + 3 + 7 = 11, which is not equal to 21. Therefore, we confirm that 21 is not a perfect number.

n = number n + 6 ======

7 and -1

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