Here's a challenge : find the shortest way to write the number $1234567890$ .
There is several ways to write the number $1234567890$ :
- $1.23456789 × 10^9$
- $2×3^2×5×3607×3803$
- $617283945×2$
But all these notations are longer. Can you find a shorter notation than $1234567890$ ?
EDIT : For this question, the length of a notation is given by the number of characters used to write the notation on a sheet of paper.
eg : $2×3^2×5×3607×3803$ is 16 chars long.
How about: $\displaystyle\sum_{i=1}^{9}i\;10^{10-i}$
Alternatively, how about $123\cdots90$? It's only $8$ characters long!
(or the $7$ character $12\cdots90$ if you find the pattern unambiguous enough)