7400

Number
$7400$ (seven thousand, four hundred) is:
 * $2^3 \times 5^2 \times 37$


 * The $50$th octagonal number, after $1$, $8$, $21$, $40$, $65$, $\ldots$, $5985$, $6256$, $6533$, $6816$, $7105$:
 * $7400 = \displaystyle \sum_{k \mathop = 1}^{50} \left({6 k - 5}\right) = 50 \left({3 \times 50 - 2}\right)$