7777

Number
$7777$ (seven thousand, seven hundred and seventy-seven) is:


 * $7 \times 11 \times 101$


 * The $16$th Kaprekar number after $1, 9, 45, 55, 99, 297, 703, 999, 2223, 2728, 4879, 4950, 5050, 5292, 7272$:
 * $7777^2 = 60 \, 481 \, 729 \to 6048 + 1729 = 7777$