How to use localized number in Flutter? 

To use localized numbers in Flutter, you can use the NumberFormat class from the intl package. This class provides methods for formatting and parsing numbers based on the user's locale.

To format a number in a specific locale, you can create an instance of the NumberFormat class with the desired locale, and then use the format method to format the number. Here's an example of formatting a number in English and German:

double number = 123456.789;

String formattedNumberEn = NumberFormat.decimalPattern('en').format(number);
print(formattedNumberEn); // 123,456.789

String formattedNumberDe = NumberFormat.decimalPattern('de').format(number);
print(formattedNumberDe); // 123.456,789

You can also format numbers in your localization messages using either the gen_l10n or Flutter Intl approaches and generated localization code will handle that for you. Here is an example of such a message in ARB file:

"pageHomeSampleTotalAmount": "Total: {total}",
"@pageHomeSampleTotalAmount": {
  "placeholders": {
    "total": {
      "type": "double",
      "format": "currency",
      "optionalParameters": {
        "symbol": "€",
        "decimalDigits": 2
      }
    }
  }
}