const str = '7320129001658066';

const multiplication = (str, multi = []) => {
  let counter = 0;
  return str
    .split('')
    .reduce((accumulator, currentValue) => {
      accumulator.push(
        multi[counter] ?
          parseInt(currentValue) * parseInt(multi[counter]) :
          parseInt(currentValue)
      );
      counter++;
      return accumulator;
    }, [])
    .join('');
};

multiplication(str, '7,3,1'.split(','));

const [number] = `${0.5}`.split('.').reverse();