In the database of Mathematical Reviews that has gained reputation in the world, the “Erdos number” is calculated for every mathematician (See: http://www.ams.org/mathscinet/collaborationDistance.html).
Erdos number shows how is a mathematician close to famous Hungarian mathematician Paul Erdos as a coauthor. Paul Erdos is considered as a scientist who is very cooperative with other known scientists. The number of his coauthors is 511. By definition the Erdos number of these scientists is taken 1. The Erdos number of the scientist who coauthored with other scientist whose Erdos number is 1, is 2, etc. Currently, there are a lot of papers devoted to the Erdos number and published in authorative journals. According to the results of “The Erdos Number Project” of Oakland University in the USA the Erdos number of well-known mathematicians is rather small. For example, the Erdos number of mathematicians awarded the Fields medal in averge equals 3 (see “Erdos Number” Wikipedia). We should note that in “The Erdos Number Project” of Oakland University the Erdos number of all famous prize-holders (Fields, Wolf, Abel, Seele, etc.) were shown in the form of separate lists (see: https://wwwp.oakland.edu/enp/erdpaths/).
According to information of Mathematical Reviews database American Mathematical Society for this year the Erdos number of the head of “Functions Theory” of IMM ANAS Vuagr Ismayilov was equal to 2. The list of AScinetists whose Erdos number doesn’t exceed 2 is located in the website of Oakland University (see:https://files.oakland.edu/users/grossman/enp/ErdosA.html) and Vugar Ismayilov’s name is in this list.
Every mathematician may calculate his Erdos number by pressing the Use Erdos in the database of Mathematical Reviews in the website http://www.ams.org/mathscinet/collaborationDistance.html.