The Arabic digit one belongs to the numerals which are widely spread around the [URL /en/1F30D/ planet]. This positional counting system appeared in India in the 5th century or even earlier. The Arabs borrowed it from the Indians. Al-Khwarizmi wrote a book called "On the Indian Calculation," which helped to spread the Arabic digits. Later this counting system came to Europe through Spain. Pope Sylvester II advocated for the replacement of [URL /ru/collections/roman-numerals/ Roman numerals] with Arabic ones in the 10th century. In the 12th century, Al-Khwarizmi's book "On the Indian Calculation" was translated into Latin, which played an important role in the adoption of Arabic [URL /en/collections/numerals/ numerals].