Because there is no specific data on a global scale, it is impossible to determine which country has the largest number of piano learners. However, according to some reports and studies, some popular piano learning countries can be identified:

1. China: China is a country that attaches great importance to music education, and piano is also one of the popular musical instruments. In China, there are many piano learners, especially in big cities and developed areas.

2. America: Piano is also one of the popular musical instruments in America, especially in family music education. It is reported that more than 6 million people in the United States learn piano.

3. Japan: Japanese people have great enthusiasm and interest in music, and piano is also one of the popular musical instruments. In Japan, the popularity of piano education is also very high, and the number of learners is considerable.

4. Korea: Piano is also a very popular musical instrument in Korea. Many Koreans learn piano and get excellent results in international competitions. South Korea has a highly developed music education and cultural industry, so the piano has been widely promoted and popularized in South Korea.

Generally speaking, the number of people learning piano in the world should be very large, but the exact number cannot be determined.