52. When the number POTOП was taken as an addend 99999 times, the resulting number had the last three digits 285. What number is denoted by the word POTOП? (Identical letters represent identical digits.)
52. Taking a number as an addend 99999 times means multiplying it by 99999 or by $(100000-1)$, i.e., appending 5 zeros to the given number and subtracting the given number from the result. In this case, we have

$$
\overline{\text { ПОТОП }} 00000-\overline{\text { ПОТОП }}=\ldots 285 .
$$

From this, we get $\Pi=5, \mathrm{O}=1, \mathrm{~T}=7(10-5=5,9-8=1,9-2=7)$. Therefore, the desired number is 51715.