Telephone country code +98 is Iran, and +98 21 is the area code for Tehran.
(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.)
The country code and area code of Babol, Iran is 98, (0)111.
The country code and area code of Golestan, Iran is 98, (0)171.
Country code +98 is Iran.
Mashhad is in Iranian telephone area code 0511, which is +98 511 in international format.
There is no telephone area code 981 in North America (USA, Canada, etc.). In Mexico, area code 981 is for the city of Campeche and surrounding areas. Other countries may have a telephone area code 981 or similar. Telephone country code +98 is Iran, but there are no numbers beginning +98 1.
The country code and area code of Hamedan, Iran is 98, (0)811.
The country code and area code of Okinawa, Japan is 81, (0)98.
The country code and area code of Fars, Iran is 98, (0)711.
The country code and area code of Gilan, Iran is 98, (0)131.
The country code and area code of Hormozgan, Iran is 98, (0)761.
The country code and area code of Kerman, Iran is 98, (0)341.
The country code and area code of Khorasan, Iran is 98, (0)511.