0621 is not a country code. Numbers inside a country start like this: Orange (Moldova), Ludwigshafen (Germany), Muzaffarpur, Bihar (India), Tebing Tinggi/Sei Rampah (Indonesia) and others. The first digit 0 is the trunk prefix for domestic calls and is dropped from abroad.
Have the full number? Check it in the number lookup.
| Area or operator | From abroad | Inside the country |
|---|---|---|
 Orange · Moldova | +373 621 … | 0621 … |
 Ludwigshafen · Germany | +49 621 … | 0621 … |
| Mannheim · Germany | +49 621 … | 0621 … |
 Muzaffarpur, Bihar · India | +91 621 … | 0621 … |
 Tebing Tinggi/Sei Rampah · Indonesia | +62 621 … | 0621 … |
 Junsele · Sweden | +46 621 … | 0621 … |
 Viettel · Tanzania | +255 621 … | 0621 … |
If a number starts with +, the first 1–3 digits are the country code. If it starts with 0 (8 in Russia and Kazakhstan), it is a domestic number: an area or operator code follows, and from abroad the 0 or 8 is replaced with + and the country code. The same digits can mean different places, so where the call came from matters.