4. In a three-digit number, the digits of hundreds and units are the same. Find all such numbers, given that each of them is divisible by 15.
Solution. Since the desired number is divisible by 5, the first and last digits are equal to 5, and they cannot be equal to 0. The sum of the digits must be divisible by 3 for the number to be divisible by 3. We get that the second digit can be $2,5,8$.

Answer. $525,555,585$.