672

Number
$672$ (six hundred and seventy-two) is:


 * $2^5 \times 3 \times 7$


 * The $21$st second pentagonal number after $2$, $7$, $15$, $26$, $\ldots$, $222$, $260$, $301$, $345$, $392$, $442$, $495$, $551$, $610$:
 * $672 = \dfrac {21 \left({3 \times 21 + 1}\right)} 2$


 * The $7$th Ore number after $1$, $6$, $28$, $140$, $270$, $496$:
 * $\dfrac {672 \times \tau \left({672}\right)} {\sigma \left({672}\right)} = 8$
 * and the $5$th after $1$, $6$, $14$, $270$ whose divisors also have an arithmetic mean which is an integer:
 * $\dfrac {\sigma \left({672}\right)} {\tau \left({672}\right)} = 84$


 * The $2$nd triperfect number:
 * $\sigma \left({672}\right) = 2016 = 3 \times 672$


 * The $13$th positive integer after $128$, $192$, $256$, $320$, $384$, $432$, $448$, $480$, $512$, $576$, $640$, $648$ with $7$ or more prime factors:
 * $672 = 2 \times 2 \times 2 \times 2 \times 2 \times 3 \times 7$