399,877,410,625

Number
$399 \, 877 \, 410 \, 625$ is:


 * $5^4 \times 7 \times 11 \times 17 \times 23 \times 79 \times 269$


 * The $26$th square pyramorphic number after $1$, $55$, $5525$, $\ldots$:
 * $399 \, 877 \, 410 \, 625 = \ds \sum_{k \mathop = 1}^{10 \, 625} k^2 = \dfrac {10 \, 625 \paren {10 \, 625 + 1} \paren {2 \times 10 \, 625 + 1} } 6$


 * The $10 \, 625$th square pyramidal number:
 * $399 \, 877 \, 410 \, 625 = \ds \sum_{k \mathop = 1}^{10 \, 625} k^2 = \dfrac {10 \, 625 \paren {10 \, 625 + 1} \paren {2 \times 10 \, 625 + 1} } 6$