To run this program, use ./gradlew run -Dargs=number where number is any number from 0 to 999999999999999999999999.
(That's nine hundred ninety-nine sextillion nine hundred ninety-nine quintillion nine hundred ninety-nine quadrillion nine hundred ninety-nine trillion nine hundred ninety-nine billion nine hundred ninety-nine million nine hundred ninety-nine thousand nine hundred ninety-nine.)
Alternatively, build a distribution with ./gradlew build, extract either the .tar or .zip file in build/distributions and use the bin/numbersToEnglish script in the distribution.