Let’s analyze the pattern in the sequence:
- 1 = \( 1^1 \)
- 4 = \( 2^2 \)
- 27 = \( 3^3 \)
- 256 = \( 4^4 \)
- 3125 = \( 5^5 \)
Each term is the number raised to the power of itself (i.e., \( n^n \)).
Following the same pattern, the next number should be \( 6^6 \):
\[
6^6 = 46656
\]
Thus, the missing number is \( \boxed{46656} \).
Therefore, the correct answer is \( \boxed{3} \).