181

Number
$181$ (one hundred and eighty-one) is:


 * The $42$nd prime number


 * The $2$nd of the $13$th pair of twin primes, with $179$


 * The $9$th palindromic prime:
 * $2, 3, 5, 7, 11, 101, 131, 151, 181, \ldots$


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