4. Variant 1.

In the number, two digits were swapped, and as a result, it increased by more than 3 times. The resulting number is 8453719. Find the original number.
Answer: 1453789.

Solution. When the number 8453719 is reduced by at least 3 times, the result is a number less than 3000000. Therefore, 8 was swapped with a digit less than 3, and the only such digit is 1.