Task 4. Find the largest natural number in which any two adjacent digits, in the given order, form a number divisible by 23.
Solution. Two-digit numbers divisible by 23 are 23, 46, 69, and 92. If the number starts with 92, then the number is 923. If it starts with 69, the number is 6923. If it starts with 46, we get the number 46923. The remaining possibility is when the desired number starts with 23, and we get 23. Therefore, the desired number is 46923.