1. Given two prime numbers $p$ and $q$ whose sum is 2019. Then the value of $(p-1)^{q-1}$ is $\qquad$ .
二、1.1 or 2016.
Since the sum of two primes is odd, one of the two primes must be 2.
Therefore, $(p, q)=(2,2017)$ or $(2017,2)$.
Thus, the required value is 1 or 2016.