1,111,111,111

Number
$1 \, 111 \, 111 \, 111$ is:


 * $11 \times 41 \times 271 \times 9091$


 * The $10$th repunit after $1$, $11$, $111$, $1111$, $\ldots$, $111 \, 111 \, 111$


 * The $103$rd Kaprekar number, and the smallest with $10$ digits:
 * $1 \, 111 \, 111 \, 111^2 = 1 \, 234 \, 567 \, 900 \, 987 \, 654 \, 321 \to 123 \, 456 \, 790 + 0 \, 987 \, 654 \, 321 = 1 \, 111 \, 111 \, 111$