What country code is 00 86 138?

Country code +86 (dialed as 00 86 from many places) is the People's Republic of China, not including Hong Kong, Macau, and Taiwan.

Beijing is area code +86 10.

Shanghai is area code +86 21.

Mobile numbers begin with +86 13, +86 15, or +86 18.

Hong Kong is country code +852.

Macau is country code +853.

Taiwan is country code +886.

Numbers beginning with +86 6 were previously reserved for Taiwan, pending reunification of China, but those numbers have been released for use on the mainland, in Shandong, Guangdong, and Yunnan provinces.

(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.)