2205

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


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