Even citeren:
"The world's longest border belongs to Russia.
Of Russia's 57,000+ kilometers of border 20,139 of it border 14 different countries; North Korea, China, Mongolia, Kazakhstan, Azerbaijan, Georgia, Ukraine, Belarus, Latvia, Estonia, Finland, Norway, Lithuania, Poland.
If it wasn't for the 86 kilometers of the Bering Strait Russia would also border the United States.
The world's longest shared border is that of Canada and the United States.
Known as the International Boundary, it has a length of 8,893 kilometers and is also known as the world's longest undefended border."