5. (10 points) Please fill in the appropriate numbers in each box in the figure below, so that the vertical calculation is valid (2015 has already been filled in). The maximum value of the product in the vertical calculation is $\qquad$ .



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【Solution】Solution: According to the problem,  
First, a two-digit number multiplied by 2 results in a three-digit number that cannot be in the 200s, so it must be in the 100s. Therefore, the tens digit of the first multiplicand is 5. The units digit, when multiplied by 2, does not carry over, so it must be a number less than 4. Therefore, it must be a number between 50 and 54.

When the two-digit number is 54, the third row cannot be filled.
When the two-digit number is 53, the three-digit factor is at most 362, and the product is 19186.
When the two-digit number is 52, the three-digit factor is at most 382, and the product is 19864.
When the two-digit number is 51 or 50, there are no numbers that meet the conditions.
Therefore, the answer is: 19864