A Prime is said to be a Sophie Germain prime if both and are Prime. The first few Sophie Germain primes are 2, 3, 5, 11, 23, 29, 41, 53, 83, 89, 113, 131, ... (Sloane's A005384).

Around 1825, Sophie Germain proved that the first case of Fermat's Last Theorem is true for such primes, i.e., if
is a Sophie Germain prime, there do not exist Integers , , and different from 0 and not multiples
of such that

Sophie Germain primes of the form (which makes a Prime) correspond to the indices of composite Mersenne Numbers . Since the largest known Composite Mersenne Number is with , is the largest known Sophie Germain prime.

**References**

Dubner, H. ``Large Sophie Germain Primes.'' *Math. Comput.* **65**, 393-396, 1996.

Ribenboim, P. ``Sophie Germane Primes.'' §5.2 in *The New Book of Prime Number Records.*
New York: Springer-Verlag, pp. 329-332, 1996.

Shanks, D. *Solved and Unsolved Problems in Number Theory, 4th ed.* New York: Chelsea, pp. 154-157, 1993.

Sloane, N. J. A. Sequence
A005384/M0731
in ``An On-Line Version of the Encyclopedia of Integer Sequences.''
http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.
*The Encyclopedia of Integer Sequences.* San Diego: Academic Press, 1995.

© 1996-9

1999-05-26