35

Number
$35$ (thirty-five) is:


 * $5 \times 7$


 * The $5$th tetrahedral number, after $1, 4, 10, 20$:
 * $35 = 1 + 3 + 6 + 10 + 15 = \dfrac {5 \left({5 + 1}\right) \left({5 + 2}\right)} 6$