515. Find all natural numbers that decrease by 14 times when the last digit is erased.
$\triangle$ Let the desired number be $10 x + y$, where $x$ is the number of tens in the number, and $y$ is its last digit. Then

$$
10 x + y = 14 x, \quad y = 4 x
$$

Since $y$ is a digit, $x$ is also a digit, and does not exceed 2. Setting $x=1,2$, we find that $y=4,8$ respectively.

Answer: $14,28$.