3003

Number
$3003$ (three thousand and three) is:


 * $3 \times 7 \times 11 \times 13$


 * The $9$th palindromic triangular number after $1$, $3$, $6$, $55$, $66$, $171$, $595$, $666$.


 * The $39$th hexagonal number after $1$, $6$, $15$, $28$, $45$, $66$, $91$, $\ldots$, $2145$, $2278$, $2415$, $2556$, $2701$, $2850$:
 * $3003 = \displaystyle \sum_{k \mathop = 1}^{39} \left({4 k - 3}\right) = 39 \left({2 \times 39 - 1}\right)$