Six hundred twenty.
620
I write 620 billion as 620 billion.
Writing a number in standard form simply means to express the number in its 'normal' form. Therefore, the way you wrote the number is the standard form for 620.
0.0371
write the word form and expanded form of the number four
2118077 word form
You can write 5.24 in word form as five and twenty-four hundredths
seven and forty two one hundredths
One and sixty-five hundredths.
You can write 14.12 in word form as fourteen and twelve hundredths
Just how it has been written in the question: "Word form".
91 in word form is ninety-one.