3081

Number
$3081$ (three thousand and eighty-one) is:


 * $3 \times 13 \times 79$


 * The $78$th triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $2211$, $2278$, $2346$, $2415$, $2485$, $2556$, $2628$, $2701$, $2775$, $2850$, $2926$, $3003$:
 * $3081 = \displaystyle \sum_{k \mathop = 1}^{78} k = \dfrac {78 \times \left({78 + 1}\right)} 2$