2278

Number
$2278$ (two thousand, two hundred and seventy-eight) is:
 * $2 \times 17 \times 67$


 * The $34$th hexagonal number after $1$, $6$, $15$, $28$, $45$, $66$, $91$, $\ldots$, $703$, $780$, $861$, $946$, $1035$, $1225$, $1326$, $1431$, $1540$, $1653$, $1770$, $1891$, $2016$, $2145$:
 * $2278 = \displaystyle \sum_{k \mathop = 1}^{34} \paren {4 k - 3} = 34 \paren {2 \times 34 - 1}$


 * The $67$th triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $1326$, $1378$, $1431$, $1485$, $1540$, $1596$, $1653$, $1711$, $1770$, $1770$, $1830$, $1891$, $1953$, $2016$, $2080$, $2145$, $2211$:
 * $2278 = \displaystyle \sum_{k \mathop = 1}^{67} k = \dfrac {67 \times \paren {67 + 1} } 2$