5720

Number
$5720$ (five thousand, seven hundred and twenty) is:


 * $2^3 \times 5 \times 11 \times 13$


 * The $44$th octagonal number, after $1$, $8$, $21$, $40$, $65$, $\ldots$, $3816$, $4033$, $4256$, $4485$, $4720$, $4961$, $5208$, $5461$:
 * $5720 = \displaystyle \sum_{k \mathop = 1}^{44} \left({6 k - 5}\right) = 44 \left({3 \times 44 - 2}\right)$