101

Number
$101$ (one hundred and one) is:


 * The $26$th prime number


 * The $1$st of the $9$th pair of twin primes, with $103$


 * The upper end of the $5$th record-breaking gap between twin primes:
 * $101 - 73 = 28$


 * The $6$th palindromic prime after $2$, $3$, $5$, $7$, $11$


 * The $50$th positive integer after $2$, $3$, $4$, $7$, $8$, $\ldots$, $61$, $65$, $66$, $67$, $72$, $77$, $80$, $81$, $84$, $89$, $94$, $95$, $96$, $100$ which cannot be expressed as the sum of distinct pentagonal numbers


 * The $5$th prime number of the form $n^2 + 1$ after $2$, $5$, $17$, $37$:
 * $101 = 10^2 + 1$


 * The $7$th of $29$ primes of the form $2 x^2 + 29$:
 * $2 \times 6^2 + 29 = 101$