When you say 20,000 ( ‘Ishrun ‘Alfan ):

In English, we write the number as:

In English-speaking regions, a comma is used as a thousands separator to make the number easier to read (20,000). In many European countries, a dot (20.000) or a space (20 000) is used instead. 2. The Regional Script: Eastern Arabic Numerals

If you need to write out the number 20,000 in Arabic text (as you would on a legal document or a check), it is written as: (Pronounced: ‘Ishrun Alf) عشرون (‘Ishrun): Twenty ألفاً (Alfa): Thousand 4. 20,000 in Various Contexts