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 $6$th Thabit number after $(2)$, $5$, $11$, $23$, $47$, $95$:
 * $191 = 3 \times 2^6 - 1$


 * The $6$th Thabit prime after $2$, $5$, $11$, $23$, $47$:
 * $191 = 3 \times 2^6 - 1$


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


 * The $13$th prime number after $53$, $71$, $103$, $107$, $109$, $149$, $151$, $157$, $163$, $167$, $173$, $181$ which cannot be expressed as the difference between a power of $2$ and a power of $3$.


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

Also see

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