Power of fifteen reduced modulo seventeen

Question

Find the remainder when $15^{2021}$ is divided by $17$ .

$2$ . $15\equiv-2\pmod{17}$ and $(-2)^4=16\equiv-1$ . With $2021=4\cdot505+1$ , $15^{2021}\equiv(-1)^{505}(-2)=2$ .

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