4 ; 4*4=16 ; 4*4*4=64 ; 4*4*4*4=256 ; 4*4*4*4*4=1024
you can see Here if number of 4 in unit place is odd then unit digit will be 4 and number of 4 in unit place is even then unit digit will be 6.
Now
5 ; 5*5 =25 ; 5*5*5=125 ; 5*5*5*5=625
Here unit digit will be 5 always.
1 ; 1*1 =1 ; 1*1*1 =1 ; 1*1*1*1=1
Here unit digit will be 1 always.
(3474)1793 :- Here number of 4 in unit place is odd so unit digit will be 4.
(225)317 :- Here unit digit will be 5.
(451)491 :- Here unit place result will be 1.
So unit digit in ( 3474)1793 *( 225 )317 * ( 451 )491}
4*5*1=20
Hence unit digit in ( 3474)1793 *( 225 )317 * ( 451 )491 will be ZERO.