Poincare conjecture, one of the "seven Millennium mathematical problems", is the focus of this international congress of mathematicians. In fact, in addition to the "Seven Millennium Mathematical Problems" put forward by the Clay Institute of Mathematics in the United States at the turn of the Millennium, there are still some interesting mathematical problems in the history of mathematics that have left a deep impression on people.

First, Goldbach conjecture proposer: German teacher Goldbach; Date of filing:1742; Description: Any even number greater than 2 can be expressed as the sum of two prime numbers; Research progress: it has not been completely cracked.

Second, the proposer of Fermat's last theorem: the French mathematician Fermat; Date of submission:1637; Description: the n power of x plus the n power of y equals the n power of z, and there is no positive integer solution when n is a natural number greater than 2; Research progress: It was successfully proved by British mathematician andrew wiles and his student richard taylor in 1995.

The three-color conjecture was put forward by guthrie, a British student. Date of filing:1852; Description: each map can be painted in four colors, so that countries with the same border can be painted in different colors; Research progress: It was verified by computer at 1976.

Fourthly, the problem of girls walking was put forward by British mathematician Kirkman. Date of submission:1850; Content abstract: There are 15 girls in a student dormitory, who walk in groups of three every day. How to arrange it so that every girl can have a chance to walk with every other girl, and it happens to be once a week; Research progress: It has been proved.

Fifth, the seventh bridge problem: originated in the town of Konigsberg, Prussia (now Kaliningrad, Russia); Date of submission:1early 8th century; Description: Two tributaries of a river bypass an island, and there are seven bridges across the two tributaries. Ask a walker if he can cross every bridge, and each bridge can only be crossed once, so that the walker can return to his original place; Research progress: Swiss mathematician Euler successfully solved this problem in 1736. (According to Xinhua News Agency)