Factorise the following by prime factorisation method:

$4335$

Factorise the following by prime factorisation method:

$1080$

Factorise the following by prime factorisation method:

$13915$

Find the $\mathrm{HCF}$ of the following numbers by prime factorisation method:

$84, 120, 138$

Find the $\mathrm{HCF}$ of the following numbers by prime factorisation method:

$81, 117$

Find the $\mathrm{HCF}$ of the following numbers by prime factorisation method:

$630, 1188$

Find the $\mathrm{HCF}$ of the following numbers by division method:

$216, 1176$

Find the $\mathrm{HCF}$ of the following numbers by division method:

$2700, 1728$

Find the $\mathrm{HCF}$ of the following numbers by division method:

$768, 324$