Problem - 3238
The number $21982145917308330487013369$ is the thirteenth power of a positive integer. Which positive integer?
Let $A=21982145917308330487013369=B^{13}$.
Because $A$ has 26 digits, therefore, we must have
$$10^{25} < A < 10^{26} \implies B<100$$
Next, we can find the lower boundary of $B$ by noting
$$80^{13} < 10^{25} \implies 80 < B < 100$$
Clearly, the last digit of $B$ must be $9$. Hence, $B$ can be only $89$ or $99$. The final step is to check whether $A$ is a multiple of $9$. Clearly, it is not. Hence, $B$ can only be $\boxed{89}$.