$2.1 \times 10^{-1}$ means multiplying 2.1 by 0.1, which is the same as moving the decimal point one place to the left.

$2.1 \times 10^{-1} = 0.21$

So, the result is 0.21.

Would you like more details on how powers of ten work? Here are 5 related questions to consider:

1. What happens if you multiply by $10^{-2}$ instead of $10^{-1}$?
2. How do negative exponents affect decimal movement?
3. Can you convert $0.21$ back to scientific notation?
4. How would $2.1 \times 10^1$ compare to $2.1 \times 10^{-1}$?
5. How does multiplying by $10^0$ affect a number?

Tip: Negative exponents in scientific notation represent small numbers less than 1, while positive exponents represent larger numbers.