0821 is not a country code. Numbers inside a country start like this: Augsburg (Germany), Mysore, Karnataka (India), Sylhet (Bangladesh), Vodacom (Congo - Kinshasa) 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 |
|---|---|---|
 Augsburg · Germany | +49 821 … | 0821 … |
 Mysore, Karnataka · India | +91 821 … | 0821 … |
 Sylhet · Bangladesh | +880 821 … | 0821 … |
| Sylhet MEA · Bangladesh | +880 821 … | 0821 … |
 Vodacom · Congo - Kinshasa | +243 821 … | 0821 … |
 Telkomsel · Indonesia | +62 821 … | 0821 … |
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.