Arabic numerals, also known as Indian numerals, have this nickname because they were actually not invented by Arabs, but by ancient Indians, and then spread to Europe by Arabs, and then spread all over the world. However, mathematics has also evolved to a certain extent. For example, some people like the number nine, while others don't. Why do many Koreans dislike the number 40?

In fact, not only Koreans dislike the number four, but also China people generally dislike this number, and so do the Japanese. Because the homonym of four is death, many people think it is unlucky, and many people who attach great importance to it will avoid this number when choosing the floor of the house or some auspicious days. So if you join Korea or Japan, you will find that some floors don't have four, because everyone feels unlucky and no one will.

There is another number that many people don't like, that is, the number thirteen. In fact, this figure is very puzzling, because in a painting by Leonardo da Vinci, the thirteenth person who attended the dinner was a Jew, and this Jew betrayed Jesus for coveting thirty gold coins to lead the way for those who arrested Jesus. Jesus was crucified on the 13th, so many people didn't like the number thirteen.

There is also the number nine, which may only be hated by the Japanese, because the number nine is similar to "bitter" in Japanese pronunciation, and everyone doesn't like to live a painful or bitter life, so it is also a taboo.