Standard Form by Boxed Rockets

Are These Numbers in Standard Form?

0.511 \times 10^{-6}

No

1.94 \times 10^{4}

Yes

2.63 \times 10^{-5}

Yes

6.7 \times 10^{4}

Yes

3.74 \times 10^{6}

Yes

6.86 \times 10^{-3}

Yes