public function asSpellout($value)
    {
        if ($value === null) {
            return $this->getNullDisplay();
        }
        $value = $this->normalizeNumericValue($value);
        if ($this->_intlLoaded) {
            $f = $this->createNumberFormatter(NumberFormatter::SPELLOUT);
            if (($result = $f->format($value)) === false) {
                throw new InvalidArgumentException('Formatting number as spellout failed: ' . $f->getErrorCode() . ' ' . $f->getErrorMessage());
            }

            return $result;
        }

        throw new InvalidConfigException('Format as Spellout is only supported when PHP intl extension is installed.');
    }