Find the common factors of $81$ and $16$.

Determine the common factor

If a number which divides the other number and leaves the remainder as zero then such number is called the factor of the given number.

If a number is the factor of two or more numbers. then such a number is called a common factor.

The factors of the given numbers$81$ and $16$ are,

$$\begin{gathered} 81:1,3,9,27,81 \\ 16:1,2,4,8,16 \end{gathered}$$

On observing these factors we can conclude that,

The common factor is $\begin{array}{rcl}& & 1\end{array}$.

Hence the common factor of$81$ and $16$ is $1$.