Number to Words Converter: Spell Out Any Number in English

The integer part is split into three-digit groups from the right. Each nonzero group is spelled and tagged with its scale word (thousand, million, and so on, through decillion). The whole value is parsed as a string, never as a floating-point number, so exactness holds well past 2^53.

Hyphens join compound tens (thirty-four). In American style no "and" appears in a whole number. In British style exactly one "and" is inserted: inside a group that has both hundreds and a remainder (one hundred and five), and before a trailing sub-hundred group when a larger group is present (one million and one). "And" never sits between major groups.

After a decimal point the digits are read one at a time (three point one four), preserving the digits as typed. US check mode reads the fraction positionally as cents instead: it right-pads to two places (.5 of a dollar is 50 cents), rounds the whole amount half away from zero on the digit string before splitting dollars and cents, and prints "and NN/100 dollars" with the first letter capitalized. Ordinal mode transforms the final word (twenty-one becomes twenty-first) and applies to whole, non-negative numbers only.

Formula: short scale, grouped in threes; decimals read digit by digit

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