145. If $a + 7^{13}$ is divisible by 23, what is the smallest natural number $a$? (1) $2$ (2) $3$ (3) $4$ (4) $5$
\textbf{145.} If $a + 7^{13}$ is divisible by 23, what is the smallest natural number $a$?
(1) $2$ \hfill (2) $3$ \hfill (3) $4$ \hfill (4) $5$
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