In Number Theory, Logic, and Cryptography




This is a web site for amateurs interested in unsolved problems in number theory, logic, and cryptography. Please read the FAQ.


How to use the site:

If you're new to the site, you may like to check out the Introduction. If you plan to be a regular visitor, you might like to bookmark the What's New page. Or go straight to any of the problems listed on the left-hand side (but note that ABC and Riemann are considerably more difficult to understand than most others).


Companion discussion group:

There is a companion discussion group, https://groups.io/g/UnsolvedProblems/topics, where questions can be asked and any of the problems or potential solutions discussed.



There are monetary prizes for solutions to most of the problems on this site. For details, please see the Prizes page.



Contributions and proposed solutions can be found on the Solutions page.


How you can assist:

If you find the site interesting, please let me know. If you would like to suggest any changes, or if you find any expired links, please let me know. And, of course, if you think you've solved any of the problems, please read the FAQ, and then let me know.


Contact information:

Please email me.







This web site developed and maintained by

Tim S Roberts

Email: timro21@gmail.com





Version HostPapa 1.0