2775

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Number

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

$3 \times 5^2 \times 37$


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


Also see