677

Number
$677$ (six hundred and seventy-seven) is:


 * The $123$rd prime number


 * The $10$th prime number of the form $n^2 + 1$ after $2$, $5$, $17$, $37$, $101$, $197$, $257$, $401$, $577$:
 * $677 = 26^2 + 1$


 * The $19$th of $29$ primes of the form $2 x^2 + 29$:
 * $2 \times 18^2 + 29 = 677$