It's actually two or three words: viginti unus, viginti et unus, and unus et viginti all occur. Unus changes form to agree with the things you're counting: feminine viginti una; neuter viginti unum.
Unus
Twenty-three million, eighty-six thousand, twenty-one.
Five hundred twenty-one billion.
Thirty-eight and twenty-one thousandths is already in word form. Its number form is 38.0021.
one hundred twenty four
four hundred twenty one and five tenths
The number is twenty-four and forty-seven one hundredths.
One hundred twenty-four and six tenths.
twelve billion, three hundred twenty million, one hundred twenty thousand.
One Latin equivalent of the English word 'unity' is unitas. The Latin noun may be translated as 'unity, oneness'. Another Latin equivalent is the number 'unus', which means 'one'.
Twenty-four thousand nine hundred one.
Seven and one hundred twenty-three thousandths.