345

Number
$345$ (three hundred and forty-five) is:


 * $3 \times 5 \times 23$


 * The $15$th second pentagonal number after $2$, $7$, $15$, $26$, $40$, $57$, $77$, $100$, $126$, $155$, $187$, $222$, $260$, $301$:
 * $345 = \dfrac {15 \paren {3 \times 15 + 1} } 2$


 * The $19$th number after $1$, $3$, $22$, $66$, $70$, $81$, $94$, $115$, $119$, $170$, $210$, $214$, $217$, $265$, $282$, $310$, $322$, $343$ whose divisor sum is square:


 * The $30$th generalized pentagonal number after $1$, $2$, $5$, $7$, $12$, $15$, $\ldots$, $222$, $247$, $260$, $287$, $301$, $330$:
 * $345 = \dfrac {15 \paren {3 \times 15 + 1} } 2$


 * The $36$th sphenic number after $30$, $42$, $66$, $70$, $\ldots$, $246$, $255$, $258$, $266$, $273$, $282$, $285$, $286$, $290$, $310$, $318$, $322$:
 * $345 = 3 \times 5 \times 23$