3240

Number
$3240$ (three thousand, two hundred and forty) is:


 * $2^3 \times 3^4 \times 5$


 * The $80$th triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $2701$, $2775$, $2850$, $2926$, $3003$, $3081$, $3160$:
 * $3240 = \displaystyle \sum_{k \mathop = 1}^{80} k = \dfrac {80 \times \left({80 + 1}\right)} 2$