2205

Number
$2205$ (two thousand, two hundred and five) is:
 * $3^2 \times 5 \times 7^2$


 * The $30$th heptagonal number after $1$, $7$, $18$, $34$, $55$, $81$, $112$, $\ldots$, $1525$, $1651$, $1782$, $1918$, $2059$:
 * $2205 = \ds \sum_{k \mathop = 1}^{30} \paren {5 k - 4} = \dfrac {30 \paren {5 \times 30 - 3} } 2$


 * The $3$rd odd abundant number after $945$, $1575$:
 * $\map {\sigma_1} {2205} - 2205 = 2241 > 2205$