A term coined by John Conway to describe a number which, for some integer *n*, is the most frequently occurring difference (or "jump") between pairs of consecutive primes less than *n*. For smallish integers (at least up to 10^{12}), the only jumping champions which appear are 2, 4 and 6. It is conjectured that the only numbers which ever qualify as jumping champions are 2, 4, 6 (=2x3), 30 (=2x3x5) and so on through the list of primorials.