The product of two co-prime numbers is $117$. Their $LCM$ should be:

Find the highest common factor of $36$ and $84.$

What is the least value that should be added to $1812$ to make it divisible by $7, 11,$ and $14$?

Three bells ring together and they will ring at intervals of $6$ seconds,$7$ seconds and $8$ seconds respectively. After what interval will they again ring together? (in seconds)

Five bells begin to toll together and toll at intervals of $36, 45, 72, 81$ and $108$ seconds. After what interval of time will they keep on tolling together? (in $seconds$)

The product of two numbers is $2028$ and their $HCF$ is $13$. The number of such pairs is