1081

Number
$1081$ (one thousand and eighty-one) is:


 * $23 \times 47$


 * The $46$th triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $496$, $528$, $561$, $595$, $630$, $666$, $703$, $741$, $780$, $820$, $861$, $903$, $946$, $990$, $1035$:
 * $1081 = \ds \sum_{k \mathop = 1}^{46} k = \dfrac {46 \times \paren {46 + 1} } 2$