The $HCF$ of the smallest prime number and the smallest composite number is . . . . . . .

Use Euclid's division algorithm to find the $HCF$ of $867$ and $255$.

Using Euclid's division algorithm,find the Highest Common Factor $(HCF)$ of the following pair of numbers and determine if they are co-prime:
$847, 2160$

Find the $LCM$ and $HCF$ of $6$ and $20$ by the prime factorisation method.

For two positive integers $a$ and $b$,if $\text{HCF}(a, b) = 7$ and $\text{LCM}(a, b) = 385$,then the product $a \times b$ is:

The Least Common Multiple $(LCM)$ of the smallest prime number and the smallest composite number is . . . . . . .