3553

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


 * The $38$th heptagonal number after $1, 7, 18, 34, 55, 81, 112, \ldots, 2205, 2356, 2512, 2673, 2839, 3010, 3186, 3367$:
 * $3553 = \displaystyle \sum_{k \mathop = 1}^{38} \left({5 k - 4}\right) = \dfrac {38 \left({5 \times 38 - 3}\right)} 2$