Are These Numbers in Standard Form?

Question 1:

0.005× 10 3
No

Question 2:

0.885× 10 -6
No

Question 3:

57.8× 10 4
No

Question 4:

8.18× 10 4
Yes

Question 5:

7.26× 10 -5
Yes

Question 6:

0.651× 10 -4
No