Consider the following the following RSA public key $pk = (N, e) = (1457, 1307)$.
(a) Knowing that $187^2 \equiv 1 \pmod {1457}$ find the factorization of $N$.
(b) Given the factorization of $N$ computed above, use the CRT to decrypt the following ciphertext $c = E_{pk}(m) = 3$.
For part a) I am not sure which property of modular arithmetic can be used? I know $187$ has a multiplicative inverse $187$. I also know the Euler function. But I think I am missing how to calculate $\phi$ from this information.