Answer:
Step-by-step explanation:
[tex]21 ^n = (3 \times 7)^n[/tex]
21 has no 2 in it's prime factorization. So it can never end in 0, 2 , 4 , 6 , 8.
OR
Odd number raise to any number is always odd, Which does not include 2, 4, 6 , 8.
So [tex]21^n[/tex] does not end with 0, 2, 4 , 6 , 8.
