There are 24 hours in a day.
The 24th of December is known around the world as Christmas eve.
In googology Edit
In Greek-based number-naming systems, 24 is associated with prefix "tetraicosa-", and with prefix "quattuorviginti-" in Latin systems.
Furthermore, it is the largest number n with the following property: Let f: ℕ → ℕ, f(a) = aa. Then for every a ∈ ℕ, there is a b ∈ ℕ, such that fb+1(a) ≡ fb(a) (mod n).