4278

Number
$4278$ (four thousand, two hundred and seventy-eight) is:


 * $2 \times 3 \times 23 \times 31$


 * The $92$nd triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $3655$, $3741$, $3828$, $3916$, $4005$, $4095$, $4186$:
 * $4278 = \ds \sum_{k \mathop = 1}^{92} k = \dfrac {92 \times \paren {92 + 1} } 2$