Which of the following numbers is not written in scientific notation? 2.001 x 10^5 6.6 x 10^50 5.2 x 10^8 41.2 x 10^4

1. Check each number to see if it's in the form \( a \times 10^n \).
2. For scientific notation, \( 1 \leq a < 10 \) and \( n \) is an integer.
3. Numbers:
- 2.001 \times 10^5 is in scientific notation, as \( 1 \leq 2.001 < 10 \).
- 6.6 \times 10^{50} is in scientific notation, as \( 1 \leq 6.6 < 10 \).
- 5.2 \times 10^8 is in scientific notation, as \( 1 \leq 5.2 < 10 \).
- 41.2 \times 10^4 is not in scientific notation, as \( 41.2 \geq 10 \).

Answer: 41.2 \times 10^4