0721 is not a country code. Numbers inside a country start like this: Karlsruhe (Germany), Rajshahi (Bangladesh), Bandar Lampung (Indonesia), Tondabayashi, Osaka (Japan) 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 |
|---|---|---|
 Karlsruhe · Germany | +49 721 … | 0721 … |
 Rajshahi · Bangladesh | +880 721 … | 0721 … |
 Bandar Lampung · Indonesia | +62 721 … | 0721 … |
 Tondabayashi, Osaka · Japan | +81 721 … | 0721 … |
 Vodacom · Tanzania | +255 721 … | 0721 … |
 LycaMobile · Uganda | +256 721 … | 0721 … |
| Savanna · Uganda | +256 721 … | 0721 … |
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.