5566

Number
$5566$ (five thousand, five hundred and fifty-six) is:


 * $2 \times 11^2 \times 23$


 * The $22$nd pentagonal pyramidal number after $1, 6, 12, 40, 75, \ldots, 1470, 1800, 2176, 2601, 3078, 3610, 4200, 4851$:
 * $5566 = \displaystyle \sum_{k \mathop = 1}^{22} \dfrac {k \left({3 k - 1}\right)} 2 = \dfrac {22^2 \left({22 + 1}\right)} 2$