The characteristics of the number of "fun arithmetic" that can be divisible by 2, 3, 5, 7, 9, 11, 13

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The number that is divisible by 2 is even.

The number that is divisible by 3 must add up to three for the number of digits, such as 136,1+3+6=10, 147=1+4+7=12, can.

The digits are divisible by 5 by 0 or 5.

The characteristic of a number divisible by 7.
A number cut to the last number, and then from the number of left to subtract the number of cut twice times, so, again and again, if the final result is a multiple of 7 (including 0), then the original number will be divisible by 7.
This method is called "Cut and Subtract". This method can also be simplified to: from one number minus 7 10 times times, 20 times times, 30 times times 、...... To the remaining 100, the number can be divisible by 7 if the remainder can be divisible by 7.

The characteristic of a number divisible by 11.
Put a number from the right to the left number, the odd bit on the number and the number on the even position to add together, and then seek their difference, if the difference is a multiple of 11 (including 0), then the original number will be divisible by 11.
For example: Determine whether 491678 can be divisible by 11.
singular digits and 9+6+8=23
The and 4+1+7=12 23-12=11 of the even digit digits
Therefore, 491678 can be divisible by 11.
This method is called the "parity-and-even-difference method".
In addition to the above methods, can also be used to determine the cutting subtraction. namely: Subtract 11 from a number 10 times times, 20 times times, 30 times times ... To a count of 100 or less. If the remainder can be divisible by 11, then the original number must be divisible by 11.
Another example: Judge 583 can be divisible by 11.
The remainder of 50 times times (583-11x50=33) with 583 minus 11 is 33, 33 is divisible by 11, and 583 must be divisible by 11.

The characteristic of a number divisible by 13.
The difference between the number of the last three digits of a multi-digit number and the number of the last three digits, if divisible by 13, the multi-digit number can be divisible by 13.
For example: Determine whether 383357 can be divisible by 13.
The number of the three digits is 357, the last three digits of the previous number is 383, the difference between the two numbers is: 383-357=26,26 can be divisible by 13, therefore, 383357 must be divisible by 13.
This method also applies to judging whether a number can be divisible by 7 or 11. such as: 283679 of the last three digits is 679, the last three digits of the previous number is composed of 283,679-283=396,396 can be divisible by 11, therefore, 283679 must be divisible by 11. Still take the original number as an example, the difference between the last three digits and the first two numbers is 396,396 cannot be divisible by 7, so 283697 must not be divisible by 7.

The characteristics of the number of "fun arithmetic" that can be divisible by 2, 3, 5, 7, 9, 11, 13