601

Number
$601$ (six hundred and one) is:


 * The $110$th prime number


 * The $22$nd positive integer $n$ after $0$, $1$, $5$, $25$, $\ldots$, $145$, $149$, $245$, $265$, $365$, $385$, $485$, $505$ such that the Fibonacci number $F_n$ ends in $n$


 * The $2$nd of the $27$th pair of twin primes:
 * $601 - 599 = 2$