037 is not a country code. Numbers inside a country start like this: Nakhon Nayok/Prachin Buri/Sa Kaeo (Thailand), Kaunas (Lithuania), Krusevac (Serbia), Abaeté - MG (Brazil) 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 |
|---|---|---|
 Nakhon Nayok/Prachin Buri/Sa Kaeo · Thailand | +66 37 … | 037 … |
 Kaunas · Lithuania | +370 37 … | 037 … |
 Krusevac · Serbia | +381 37 … | 037 … |
 Abaeté - MG · Brazil | +55 37 … | 037 … |
| Araújos - MG · Brazil | +55 37 … | 037 … |
| Arcos - MG · Brazil | +55 37 … | 037 … |
| 62 more in Brazil | ||
 Tebessa · Algeria | +213 37 … | 037 … |
 Una-Sana Canton · Bosnia & Herzegovina | +387 37 … | 037 … |
 Balgarin · Bulgaria | +359 37 … | 037 … |
| Belitsa, Hask. · Bulgaria | +359 37 … | 037 … |
| Biser · Bulgaria | +359 37 … | 037 … |
| 7 more in Bulgaria | ||
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.