0421 is not a country code. Numbers inside a country start like this: Bremen (Germany), Chaoyang, Liaoning (China), Tirupur, Tamil Nadu (India), Pakruojis (Lithuania) 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 |
|---|---|---|
 Bremen · Germany | +49 421 … | 0421 … |
 Chaoyang, Liaoning · China | +86 421 … | 0421 … |
 Tirupur, Tamil Nadu · India | +91 421 … | 0421 … |
 Pakruojis · Lithuania | +370 421 … | 0421 … |
 Optus · Australia | +61 421 … | 0421 … |
 Sharsa (Benapol) · Bangladesh | +880 421 … | 0421 … |
 Parepare/Pinrang · Indonesia | +62 421 … | 0421 … |
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.