What is the biggest known safe prime number?

Question

I am looking for the biggest known safe prime number. Can someone provide some reference to what that number is and a proof that it is indeed a safe prime number?

Answer 1

$18543637900515 × 2^{666668} − 1$.

From the same link you had posted. And the proof, equate it to $2k+1$, and check whether $k$ is a prime.

If $k$ is a prime it is a Sophie Germain prime.

http://en.wikipedia.org/wiki/Sophie_Germain_prime

Answer 2

As of October $2012$, the largest known safe prime is $18543637900515\cdot2^{666668}−1$. This is paired to the biggest Sophie Germain prime number found in April $2012$, which is $18543637900515\cdot2^{666667}-1$.