What is the rightmost digit preceding the zeros in the value of 30^30?

30^30 = 3^30 × 10^30. The 10^30 contributes 30 trailing zeros. The digit preceding these zeros is the unit digit of 3^30. The cyclicity of unit digit of 3 is: 3, 9, 7, 1 (cycle of 4). 30 mod 4 = 2, so unit digit of 3^30 is 9. Hence the rightmost digit preceding the zeros is 9.