The digit in unit's place of product -
$${\left( {2464} \right)^{1793}}$$   $$ \times {\left( {615} \right)^{317}}$$   $$ \times {\left( {131} \right)^{491}}$$

$$\eqalign{ & {\left( {2464} \right)^{1793}} \times {\left( {615} \right)^{317}} \times {\left( {131} \right)^{491}} \cr & {4^1} \to 4 \to 4 \cr & {4^2} \to 16 \to 6 \cr & {4^3} \to 64 \to 4 \cr} $$
So, odd power of 4 will have 4 as unit digit and even power of 4 will have 6 as unit digit 5 and 1 have same unit digits respectively.
(2464)¹⁷⁹³ have the odd power therefore unit digit is 4
(615)³¹⁷ have unit digit 5 and
(131)⁴⁹¹ have unit digit 1.
i.e Unit digit of the product will be 4 × 5 × 1 = 20.
? 0 is the unit digit