This tag is precisely for the "[number] mi yodeya" ("who knows [number]?") series of questions originated on this site's predecessor, mi.yodeya. It started with "Echad - mi yodeya?" ("who knows one?") and continues; as of this posting it is up to "Shisha Vetishim Umatayim - mi yodeya?" ("who knows two hundred ninety-six?").
The series is patterned after a song sung at the seder.
Note that this series does not necessarily represent a good on-topic question here according to current standards but has been grandfathered in. Please take that into account before criticizing these questions or using them as precedent towards new 'series' questions.