1031

Number
$1031$ (one thousand and thirty-one) is:


 * The $173$rd prime number


 * The $40$th Sophie Germain prime after $2$, $3$, $5$, $11$, $23$, $29$, $41$, $\ldots$, $653$, $659$, $683$, $719$, $743$, $761$, $809$, $911$, $953$, $1013$, $1019$:
 * $2 \times 1031 + 1 = 2063$, which is prime.


 * The index of the $5$th repunit prime after $R_2$, $R_{19}$, $R_{23}$, $R_{317}$