191

Number
$191$ (one hundred and ninety-one) is:


 * The $43$rd prime number


 * The $1$st of the $14$th pair of twin primes, with $193$


 * The $15$th Sophie Germain prime after $2, 3, 5, 11, 23, 29, 41, 53, 83, 89, 113, 131, 173, 179$:
 * $2 \times 191 + 1 = 383$, which is prime.


 * The $10$th palindromic prime:
 * $2, 3, 5, 7, 11, 101, 131, 151, 181, 191, \ldots$


 * The larger of the $2$nd pair of primes whose prime gap is $10$:
 * $191 - 181 = 10$


 * The $10$th of $29$ primes of the form $2 x^2 + 29$:
 * $2 \times 9^2 + 29 = 191$