051 is not a country code. Numbers inside a country start like this: Azercell (Azerbaijan), Wecom (Israel), Alvorada - RS (Brazil). 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 |
|---|---|---|
 Azercell · Azerbaijan | +994 51 … | 051 … |
 Wecom · Israel | +972 51 … | 051 … |
| Xphone · Israel | +972 51 … | 051 … |
 Alvorada - RS · Brazil | +55 51 … | 051 … |
| Amaral Ferrador - RS · Brazil | +55 51 … | 051 … |
| Anta Gorda - RS · Brazil | +55 51 … | 051 … |
| 74 more in Brazil | ||
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.