I don't know any way to look it up historically, but at time of posting the current weeks champions total is 6 people.

Any idea if it has ever been 7? I think historically there has been a small number of very dominant solvers, so it feels unlikely perhaps...

Side note, I wonder if it might be nice to have a counter in the personal stats of number of times you were number 1 when the puzzle locks for the week.

I just checked and in fact it happened yesterday - 7 different players in the number 1 spot:

oyvind, Tilps, Stephen, pqg, matth314, puzzlescot, jaku111

I can't see it happening before yesterday, from a quick glance through the stats.