7777

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


 * $7 \times 11 \times 101$


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