3486

Number
$3486$ (three thousand, four hundred and eighty-six) is:


 * $2 \times 3 \times 7 \times 83$


 * The $42$nd hexagonal number after $1$, $6$, $15$, $28$, $45$, $66$, $91$, $\ldots$, $2145$, $2278$, $2415$, $2556$, $2701$, $2850$, $3003$, $3160$, $3321$:
 * $3486 = \displaystyle \sum_{k \mathop = 1}^{42} \paren {4 k - 3} = 42 \paren {2 \times 42 - 1}$


 * The $83$rd triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $2701$, $2775$, $2850$, $2926$, $3003$, $3081$, $3160$, $3240$, $3321$, $3403$:
 * $3486 = \displaystyle \sum_{k \mathop = 1}^{83} k = \dfrac {83 \times \paren {83 + 1} } 2$