870

Number
$870$ (eight hundred and seventy) is:


 * $2 \times 3 \times 5 \times 29$


 * The magic constant of a magic square of order $12$, after $1$, $(5)$, $15$, $34$, $65$, $111$, $175$, $260$, $369$, $505$, $671$:
 * $870 = \ds \dfrac 1 {12} \sum_{k \mathop = 1}^{12^2} k = \dfrac {12 \paren {12^2 + 1} } 2$