126

Number
$126$ (one hundred and twenty-six) is:


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


 * The $6$th pentagonal pyramidal number after $1, 6, 12, 40, 75$:
 * $126 = 1 + 5 + 12 + 22 + 35 + 51 = \dfrac {6^2 \left({6 + 1}\right)} 2$


 * The $9$th second pentagonal number after $2, 7, 15, 26, 40, 57, 77, 100$:
 * $126 = \dfrac {9 \left({3 \times 9 + 1}\right)} 2$


 * The $18$th generalized pentagonal number after $1, 2, 5, 7, 12, 15, 22, 26, 35, 40, 51, 57, 70, 77, 92, 100, 117$:
 * $126 = \dfrac {9 \left({3 \times 9 + 1}\right)} 2$


 * The $6$th pentatope number after $1, 5, 15, 35, 70$:
 * $126 = 1 + 4 + 10 + 20 + 35 + 56 = \dfrac {6 \left({6 + 1}\right) \left({6 + 2}\right) \left({6 + 3}\right)} {24}$


 * The $4$th even integer that cannot be expressed as the sum of $2$ prime numbers of which the smaller one is $3$, $5$ or $7$.