505

Number
$505$ (five hundred and five) is:


 * $5 \times 101$


 * The magic constant of the order $10$ magic square:
 * $505 = \dfrac {10 \left({10^2 + 1}\right)} 2$


 * The magic constant of a magic square of order $10$, after $1$, $(5)$, $15$, $34$, $65$, $111$, $175$, $260$, $369$:
 * $505 = \displaystyle \dfrac 1 {10} \sum_{k \mathop = 1}^{10^2} k = \dfrac {10 \paren {10^2 + 1} } 2$