3553

Number
$3553$ (three thousand, five hundred and fifty-three) is:
 * $11 \times 17 \times 19$


 * The $38$th heptagonal number after $1$, $7$, $18$, $34$, $5$, $81$, $112$, $\ldots$, $2205$, $2356$, $2512$, $2673$, $2839$, $3010$, $3186$, $3367$:
 * $3553 = \displaystyle \sum_{k \mathop = 1}^{38} \left({5 k - 4}\right) = \dfrac {38 \left({5 \times 38 - 3}\right)} 2$