Check whether the given number is divisible by $21$.

$21063$

Check whether the following number is divisible by $21$.

$20163$

Without actual division show that $11$ is a factor of $1111$.

Without actual division show that $11$ is a factor of $11011$.

Without actual division show that $11$ is a factor of $110011$.

Without actual division show that $11$ is a factor of $1100011$.

Without actual division show that $55$ is divisible by $5$.

Without actual division show that $555$ is divisible by $5$.

Without actual division show that $5555$ is divisible by $5$.