**404**= 2

^{2}x 101.

**404**is a number that is the product of a prime and the square of a different prime.

The numbers 199989

^{394}, 199989

^{404}and 199989

^{464}begin with the digits 394,

**404**, and 464 respectively.

**404**has a representation as a sum of two squares:

**404**= 20

^{2}+ 2

^{2}.

**404**is the sum of seven positive fifth powers:

**404**= 1

^{5}+ 2

^{5}+ 2

^{5}+ 2

^{5}+ 2

^{5}+ 2

^{5}+ 3

^{5}.

**404**is the HTTP status code for "file not found," perhaps the most famous HTTP status code.

Source: Number Gossip