In order to make 51 () fill in this number, it has both factor 2 and factor 3. What number can () fill in

In order to make 51 () fill in this number, it has both factor 2 and factor 3. What number can () fill in

You can fill in 0 and 6
Analysis: if the number has a factor of 2, it is a multiple of 2, so the number on the individual bit can be 0, 2, 4, 6, 8;
If the number has a factor of 3, then it is a multiple of 3. Therefore, the sum of the number in a digit plus 1 in ten and 5 in a hundred must be divisible by 3, then the numbers that can be added are 0, 3, 6 and 9,
To sum up, the numbers that can be filled in () can only be 0 and 6