12345 is an Arabic numeral; There were Roman numerals before; The number of Chinese characters is 12345, and the corresponding Chinese characters are capitalized as one, two, three, four and five.

1, an Arabic numeral, is an internationally used number at present. It was first invented by Indians, then spread to Europe by Arabs, and then modernized by Europeans. Because of the spread of Arabs, it has become a key node in the international use of such numbers, so people call it "Arabic numerals". Arabic numerals consist of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 * * * 10 counting symbols. Take the position value method, the high position is on the left, the low position is on the right, and the writing is from left to right. With the help of some simple mathematical symbols (decimal point, minus sign, percent sign, etc. ), this system can clearly represent all rational numbers. In order to express extremely large or extremely small numbers, people have created scientific notation on the basis of Arabic numerals.

2. Roman numerals were used in Europe before the introduction of Arabic numerals (actually Indian numerals), but they are rarely used now. It came into being later than China's figures and Oracle Bone Inscriptions's, and even later than Egyptian decimal figures. However, its appearance marks the progress of an ancient civilization.