7770

Previous  ... Next

Number

$7770$ (seven thousand, seven hundred and seventy) is:

$2 \times 3 \times 5 \times 7 \times 37$

The $35$th tetrahedral number, after $1$, $4$, $10$, $20$, $35$, $\ldots$, $3276$, $3276$, $4060$, $4495$, $4960$, $5456$, $5984$, $6545$, $7140$:

$7770 = \ds \sum_{k \mathop = 1}^{35} \frac {k \paren {k + 1} } 2 = \dfrac {35 \paren {35 + 1} \paren {35 + 2} } 6$

Also see

• Previous  ... Next: Tetrahedral Number