4. The remainder of $\left(17^{2015}-2\right) \div 15$ is
【Answer】6
【Analysis】Remainder: Computability
Since, $17^{2015} \equiv 2^{2015}(\bmod 15), 2^{4} \equiv 1(\bmod 15)$,
Therefore, $2^{2015} \equiv 2^{3} \equiv 8(\bmod 15),\left(17^{2015}-2\right) \equiv(8-2) \equiv 6(\bmod 15)$
The remainder is 6.