1. The problem asks: What is the world's most difficult math problem? 2. There is no single universally agreed "most difficult" math problem, but historically, some problems have been famously challenging, such as the Riemann Hypothesis, P vs NP, and the Navier-Stokes existence and smoothness problem. 3. For example, the Riemann Hypothesis concerns the distribution of prime numbers and is stated as: all non-trivial zeros of the Riemann zeta function have real part $\frac{1}{2}$. 4. These problems are part of the Millennium Prize Problems, each with a million-dollar prize for a correct solution. 5. Since the question is about difficulty rather than a specific problem to solve, the answer is descriptive rather than computational. Final answer: The world's most difficult math problems are considered to be the Millennium Prize Problems, including the Riemann Hypothesis, P vs NP, and others, which remain unsolved and are central challenges in mathematics.