Today I was invited to give a short lecture on the occasion of the award ceremony for the Swiss Mathematical Olympiads (the national olympiads from which the Swiss participants to the International Mathematical Olympiad are selected). So I talked (of course…) about prime numbers. I’ve put the presentation on the web (it is in French, but of course there is only a minimal amount of text so it should be fairly understandable; if there’s any interest, I’ll prepare an English translation).