521/Historical Note

Historical Note on $521$
The Mersenne number $2^{521} - 1$ was proven to be the $13$th Mersenne prime on $30$th January $1952$, on the Standards Western Automatic Computer.

The program used was written by over the Christmas period of $1951$, using an implementation of the Lucas-Lehmer Test.

This and the $14$th Mersenne prime $2^{607} - 1$ were thus discovered after a mere few hours.