The country code 543 does not correspond to any specific country. Country codes are assigned by the International Telecommunication Union (ITU) and typically consist of one to three digits. It is possible that 543 may be a typographical error or a non-standard code used in a specific context, but it is not recognized as a standard country code in the ITU's official list.
If you are referring to telephone country codes, then there is no country with code 543.
Within Agentina (country code 54), if the next digit is a 3, ie you have dialled +543, then further digits dialled will give a number in:
+54 30 - a mobile phone
+54 32 - a mobile phone
+54 33 - a mobile phone
+54 341 - Rosario
+54 342 - Santa Fe
+54 351 - Cordoba
+54 352 - Cordoba
+54 361 - Mendoza
+54 3627 - San Rafael
+54 364 - San Juan
+54 3722 - Resistenci
+54 3752 - Posadas
+54 3783 - Corrientes
54 is Argentina, so I don't think there is a separate "543" country code. The "3" would probaby refer to some region within Argentina.
The country code and area code of Winterswijk, Netherlands is 31, (0)543.
The country code and area code of Chakwal, Pakistan is 92, (0)543.
The country code and area code of Tambul, Sudan is 249, (0)543.
The country code and area code of Binzhou- SD, China is 86, (0)543.
The country code and area code of Ihara District- Shizuoka, Japan is 81, (0)543.
543 849 1792
543
543
543 is not prime. 543 = 3 * 181
543
543
543 + 78900000 = 78900543