345

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


 * $3 \times 5 \times 23$


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


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


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


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