Pengő was introduced in Hungary as national currency on December 30, 1926 and was the part of the world's biggest hyperinflation ever.
After the end of the World War II the inflation in Hungary was 4.19x 1016percent per month. It meaned that the prices doubled every 15 hours. Before 1945, the highest denomination was 1,000 Pengő. By the end of 1945, it was 10,000,000 Pengő. But the highest denomination in mid-1946 was 100,000,000,000,000,000,000 (100 quintillion) Pengő. In addition, one sextillion (1021) Pengő was also printed but was never issued. The Hungarian economy could only be stabilized by the introduction of a new currency. So on August 1, 1946, the Forint which is still used (till 2012?) was introduced at a rate of 400,000,000,000,000,000 000,000,000,000 (400 octillion - 4x1029) Pengő.