2870

Number
$2870$ (two thousand, eight hundred and seventy) is:


 * $2 \times 5 \times 7 \times 41$


 * The $20$th square pyramidal number after $1$, $5$, $14$, $30$, $55$, $\ldots$, $1015$, $1240$, $1496$, $1785$, $2109$, $2470$:
 * $2870 = \displaystyle \sum_{k \mathop = 1}^{20} k^2 = \dfrac {20 \left({20 + 1}\right) \left({2 \times 20 + 1}\right)} 6$