If (21121)3 = (C)4, then what is the value of C?

Explanation

(21121)₃ = 2 × 81 + 1 × 27 + 1 × 9 + 2 × 3 + 1 = 205. Converting 205 to base 4 gives 3 × 64 + 0 × 16 + 3 × 4 + 1 = (3031)₄.