673

Number
$673$ (six hundred and seventy-three) is:


 * The $122$nd prime number


 * The $15$th Proth prime after $3$, $5$, $13$, $17$, $41$, $97$, $113$, $193$, $241$, $257$, $353$, $449$, $577$, $641$:
 * $673 = 21 \times 2^5 + 1$


 * The $41$st left-truncatable prime after $2$, $3$, $5$, $7$, $\ldots$, $443$, $467$, $523$, $547$, $613$, $617$, $643$, $647$, $653$