2775

Number
$2775$ (two thousand, seven hundred and seventy-five) is:


 * $3 \times 5^2 \times 37$


 * The $74$th triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $2211$, $2278$, $2346$, $2415$, $2485$, $2556$, $2628$, $2701$:
 * $2775 = \displaystyle \sum_{k \mathop = 1}^{74} k = \dfrac {74 \times \paren {74 + 1} } 2$