PS Archive | Re: What is the remainder of 13^81 when divided by 10?

13^81 mod 10

13 mod 10 = 3

13^2 mod 10 = 9

13^3 mod 10 = 7

13^4 mod 10 = 1

13^5 mod 10 = 3

so we can a cycle of 4

3,9,7,1 for last digit

and thus 81 = 4k+1

so 13 mod 10 and 13^81 mod 10 will have same last digit

1

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