703

Number
$703$ (seven hundred and three) is:


 * $19 \times 37$


 * The $37$th triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $325$, $351$, $378$, $406$, $435$, $465$, $496$, $528$, $561$, $595$, $630$, $666$:
 * $703 = \displaystyle \sum_{k \mathop = 1}^{37} k = \dfrac {37 \times \left({37 + 1}\right)} 2$


 * The $19$th hexagonal number after $1, 6, 15, 28, 45, 66, 91, \ldots, 378, 435, 496, 561, 630$:
 * $703 = \displaystyle \sum_{k \mathop = 1}^{19} \left({4 k - 3}\right) = 19 \left({2 \times 19 - 1}\right)$


 * The $7$th Kaprekar number after $1, 9, 45, 55, 99, 297$:
 * $703^2 = 494 \, 209 \to 494 + 209 = 703$