Standard Form by Boxed Rockets

Are These Numbers in Standard Form?

5.36 \times 10^{-6}

Yes

0.67 \times 10^{-6}

No

4.89 \times 10^{-4}

Yes

0.2 \times 10^{4}

No

8.4 \times 10^{6}

Yes

6.02 \times 10^{3}

Yes