35

Number
$35$ (thirty-five) is:


 * $5 \times 7$


 * The $13$th semiprime after $4, 6, 9, 10, 14, 15, 21, 22, 25, 26, 33, 34$:
 * $35 = 5 \times 7$


 * The $5$th pentagonal number after $1, 5, 12, 22$:
 * $35 = 1 + 4 + 7 + 10 + 13 = \dfrac {5 \left({3 \times 5 - 1}\right)} 2$


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