431

Number
$431$ (four hundred and thirty-one) is:


 * The $83$rd prime number


 * The $1$st of the $23$rd pair of twin primes:
 * $433 - 431 = 2$


 * The $23$rd Sophie Germain prime after $2$, $3$, $5$, $11$, $23$, $29$, $41$, $53$, $83$, $89$, $113$, $131$, $173$, $179$, $191$, $233$, $239$, $251$, $281$, $293$, $359$, $419$:
 * $2 \times 431 + 1 = 863$, which is prime.