Chapter 5 - Number Theory and the Real Number System - 5.1 Number Theory: Prime and Composite Numbers - Exercise Set 5.1 - Page 256: 83

13 is not a Germain prime.

A prime number $p$ is a Germain prime if $2p+1$ is also a prime. This means that 13 is a Germain prime if: $2(13)+1$ is also a prime number. Note that $2(13)+1=27$, which is not a prime number. Thus, 13 is not a Germain prime.