98. It is known that the numbers $\overline{\mathrm{aB}^{\mathrm{B}}}, \overline{\mathrm{ac}}$ and $\overline{\mathrm{aa}}-1$ are prime. Find these numbers.
98. Since $\overline{a a}-1$ is a prime number, then $a$ is an even number. Among the numbers of the form $\overline{a a}-1$, the only prime number is $44-1=43$. Then $\overline{a b}=41, \overline{a c}=47$.