621,770

Number
$621,770$ (six hundred and twenty-one thousand, seven hundred and seventy) is:


 * $2 \times 5 \times 97 \times 641$


 * The $2$nd rare number after $65$:
 * $621 \, 770 + 077 \, 126 = 836^2$, $621 \, 770 - 077 \, 126 = 738^2$