There is no area code 529 in Mexico. It is unassigned.
However, Mexico uses international telephone country code +52, and area codes beginning with 9 are in the southernmost part of the country. For example, the area code for the city of Oaxaca is 951. Landline numbers in Oaxaca are +52 951; mobile phone numbers from Oaxaca are +52 1 951.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
There is no area code 523 in North America (USA, Canada, etc.). International country code +52 is Mexico.
There is no area code 678 in Mexico.
The country code and area code of Dafnia, Libya is 218, (0)523.
The country code and area code of Dedemsvaart, Netherlands is 31, (0)523.
The country code and area code of Lysekil, Sweden is 46, (0)523.
The country code and area code of Taizhou- JS, China is 86, (0)523.
The country code and area code of Gharia 10, Sudan is 249, (0)523.
505 is the area code for Zuni, New Mexico.
The country code and area code of Abasolo, Mexico is 52, (01)429.
The country code and area code of Acacoyagua, Mexico is 52, (01)918.
The country code and area code of Acambaro, Mexico is 52, (01)417.
The country code and area code of Acambay, Mexico is 52, (01)718.