911

Number
$911$ (nine hundred and eleven) is:


 * The $156$th prime number


 * The $36$th Sophie Germain prime after $2$, $3$, $5$, $11$, $23$, $29$, $41$, $\ldots$, $431$, $443$, $491$, $509$, $593$, $641$, $653$, $659$, $683$, $719$, $743$, $761$, $809$:
 * $2 \times 911 + 1 = 1823$, which is prime.


 * The $22$nd of $29$ primes of the form $2 x^2 + 29$:
 * $2 \times 21^2 + 29 = 911$