"$150,000 to the first individual or group who discovers a prime number with at least 100,000,000 decimal digits"
https://www.eff.org/awards/coop
Could be a fun Rust project to learn. But I don't know Rust so maybe too tricky.
Discussion
But holy cow
>"a prime number with at least 100,000,000 decimal digits (i.e., a prime integer > 10⁹⁹⁹⁹⁹⁹⁹⁹)"