Should I mention irrelevant educational achievements?

You don't have to mention everything.

But most employers are going to ask about this one anyway. Plus, for some employers having achieved a degree in any field of study is an indicator of the prospective employees persistence and stamina. So I'd put it down.

It is good to mention a university degree even if it does not apply to your job. The degree shows your academic accomplishment.

Your degree makes you more competitive against someone with a similar background and no degree.

Thank yo for your answers, Steven Parker, Peter Vanderlind de Oliveira, edwardr !

You helped me to decide and I put my University degree into resume. There were just two relevant courses: math and math-statistics. And I mentioned it.

You might think it's completely irrelevant, but the employer might not think so.

If you read the biography of some successful people, you're gonna notice that some of them were able to incorporate into the their new field of work the knowledge they got from the university, even though the degree wasn't directly linked to job.