Question 487120
Same units digits as 7^n. 7^1 ≡ 7 (mod 10), 7^2 ≡ 9, 7^3 ≡ 3, 7^4 ≡ 1, 7^5 ≡ 7, and the pattern repeats. The only possible digits are 1,3,7,9.