P versus NP Hodge conjecture.
Riemann hypothesis.
Yang–Mills existence and mass gap.
Navier–Stokes existence and smoothness.
Birch and Swinnerton-Dyer conjecture.

wow yes, very interesting question. i think that the answer is 5

Step-by-step explanation:

The Millennium Prize Problems are seven problems in mathematics that were stated by the Clay Mathematics Institute on May 24, 2000.[1] The problems are the Birch and Swinnerton-Dyer conjecture, Hodge conjecture, Navier–Stokes existence and smoothness, P versus NP problem, Poincaré conjecture, Riemann hypothesis, and Yang–Mills existence and mass gap. A correct solution to any of the problems results in a US$1 million prize being awarded by the institute to the discoverer(s).

To date, the only Millennium Prize problem to have been solved is the Poincaré conjecture, which was solved in 2003 by the Russian mathematician Grigori Perelman. He declined the prize money.