7140

Number
$7140$ (seven thousand, one hundred and forty) is:


 * $2^2 \times 3 \times 5 \times 7 \times 17$


 * The $119$th triangular number:
 * $7140 = \displaystyle \sum_{k \mathop = 1}^{119} k = \dfrac {119 \times \left({119 + 1}\right)} 2$


 * The $60$th hexagonal number after $1$, $6$, $15$, $28$, $45$, $66$, $91$, $\ldots$, $5565$, $5778$, $5995$, $6216$, $6441$, $6670$, $6903$:
 * $7140 = \displaystyle \sum_{k \mathop = 1}^{60} \left({4 k - 3}\right) = 60 \left({2 \times 60 - 1}\right)$


 * The $34$th tetrahedral number, after $1$, $4$, $10$, $20$, $35$, $\ldots$, $3276$, $3276$, $4060$, $4495$, $4960$, $5456$, $5984$, $6545$:
 * $7140 = \displaystyle \sum_{k \mathop = 1}^{34} \frac {k \left({k + 1}\right)} 2 = \dfrac {34 \left({34 + 1}\right) \left({34 + 2}\right)} 6$


 * The $5$th and last after $1$, $10$, $120$, $1540$ of the $5$ tetrahedral numbers which are also triangular.