An integer consists of 7 different digits, and is a multiple of each of its digits.
What digits are in this nubmer?
Problem 1162
Official solution
1. Identify the digits that cannot be in the number:
- Digit 0: If 0 were a digit of , then would not be a multiple of 0 (since division by zero is undefined). Therefore, 0 cannot be a digit of .
- Digit 5: If 5 were a digit of , then must end in 5 to be divisible by 5 (since 0 is not a digit). This would make odd, and thus cannot have any even digits, which is impossible since we need 7 different digits. Therefore, 5 cannot be a digit of .
- Digit 4: If 4 were a digit of , then we need to check the sum of the digits to ensure it is a multiple of 3 and 9. Removing any one digit from and adding 4 does not result in a sum that is a multiple of 9. Therefore, 4 cannot be a digit of .
2. Determine the remaining digits:
- The remaining digits are .
3. Verify the construction:
- A valid construction of using these digits is .
- Check if is divisible by each of its digits:
- (divisible)
- (divisible)
- (divisible)
- (divisible)
- (divisible)
- (divisible)
- (divisible)
Since is divisible by each of its digits, the construction is valid.
The final answer is .