It is 1.000021
It is 1.000021 if you mean 1 and 21 millionths or 1.000020 if you mean 1 and 20 one-millionths.
Twenty one millionths (0.000021) in standard form is 2.1 × 10-5
0.00002
One and twenty one millionths (1.000021) in standard form is: 1.000021 × 100
Seventeen and two hundred twenty millionths (17.00022*) in standard form = 1.700022 × 101*this is the standard notation
0.000020
9.00002
.000005
396 millionths in decimal form = 0.000396
To write eight hundred thousand and forty-two millionths in standard form, you would use the decimal form. It would be written as 0.800042.
300 millionths can be written in standard form as 0.0003
Fifty millionths in standard form is 0.000050