197

Number
$197$ (one hundred and ninety-seven) is:


 * The $45$th prime number


 * The $6$th prime number of the form $n^2 + 1$ after $2$, $5$, $17$, $37$, $101$:
 * $197 = 14^2 + 1$


 * The $7$th Keith number after $14$, $19$, $28$, $47$, $61$, $75$:
 * $1$, $9$, $7$, $17$, $33$, $57$, $107$, $197$, $\ldots$


 * The smaller of the $15$th pair of twin primes, with $199$


 * The $20$th left-truncatable prime after $2$, $3$, $5$, $7$, $13$, $17$, $23$, $37$, $43$, $47$, $53$, $67$, $73$, $83$, $97$, $113$, $137$, $167$, $173$

Also see