7

This number is a prime.

Single Curio View: (Seek other curios for this number)

There are 7² natural numbers n such that n is equal to the number of 7's in the decimal digits of all numbers smaller or equal to n. [Capelle]

Submitted: 2009-06-25 11:58:16; Last Modified: 2009-06-25 13:52:44.