2600

Number
$2600$ (two thousand six hundred) is:
 * $2^3 \times 5^2 \times 13$


 * The $24$th tetrahedral number, after $1$, $4$, $10$, $20$, $35$, $\ldots$, $816$, $969$, $1140$, $1330$, $1540$, $1771$, $2024$, $2300$:
 * $2600 = \ds \sum_{k \mathop = 1}^{24} \frac {k \paren {k + 1} } 2 = \dfrac {24 \paren {24 + 1} \paren {24 + 2} } 6$