The five euro note (symbol: € 5) is the lowest denomination of the euro note banknote used since the introduction of the euro (in its cash form) in 2002. Twenty-five countries (legally 23) are using it as their sole currency. As of 2015, its population is over 338 million. It is the smallest of the Euro notes with a size of 120 x 72 mm and a gray line. The five euro banknotes depict the classical architectural architecture (up to the fifth century) and arched arches / entrances. The five euro banknotes have a variety of security features, such as watermarks , invisible ink , holograms and microprinting, as well as proof of the authenticity of the document. As of September 2015 , there are approximately 1,808,484,228 five euro banknotes in the eurozone . The euro was established on January 1 , 1999 as the currency of more than 300 million people in Europe. For the first three years the euro existed as an invisible currency , used only in accounting. On January 1 , 2002, the euro was introduced by replacing the national banknotes and coins of 12 eurozone countries, such as the Irish Pound , the Deutsche Mark and the Italian Lira, at a fixed conversion rate. Of the current 28 member states of the European Union, 19 are using euro banknotes and coins as legal tender. The micro-states of Andorra , Monaco , San Marino and Vatican City are using the euro on a formal basis with the European Community.