# If p is an odd prime, then $2^{p-1} \equiv p+1 \bmod 2p$

If $p$ is an odd prime, then $2^{p-1} \equiv p+1 \bmod 2p$.

I can't seem to apply Fermat's Little Theorem with this one. Can anyone give me a hint on how to prove this.

You can use the Chinese remainder theorem in this case, since $2$ and $p$ are relatively prime. You clearly have $2^{p-1} \equiv 0$ mod $2$ and $2^{p-1} \equiv 1$ mod $p$, by Fermat's little theorem. Now, using the CRT, you can find the class of $2^{p-1}$ mod $2p$.
Or from $$2^{p-1}\equiv 0 \pmod{2} \Rightarrow 2^{p-1}\equiv p+1 \pmod{2}$$ since $p+1$ is even. And $$2^{p-1}\equiv 1 \pmod{p} \Rightarrow 2^{p-1}\equiv p+1 \pmod{p}$$ Or $$2 \mid (2^{p-1}-(p+1))$$ $$p \mid (2^{p-1}-(p+1))$$ and $\gcd(2,p)=1$, thus $$2p \mid (2^{p-1}-(p+1)) \Rightarrow 2^{p-1}\equiv p+1 \pmod{2p}$$