3940

Number
$3940$ (three thousand, nine hundred and forty) is:
 * $2^2 \times 5 \times 197$


 * The $40$th heptagonal number after $1$, $7$, $18$, $34$, $55$, $81$, $112$, $\ldots$, $2205$, $2356$, $2512$, $2673$, $2839$, $3010$, $3186$, $3367$, $3744$:
 * $3940 = \ds \sum_{k \mathop = 1}^{40} \paren {5 k - 4} = \dfrac {40 \paren {5 \times 40 - 3} } 2$