What's the notation for writing a number as its digits Hoping this is a simple question, I'm pretty certain this is covered in number theory, but I haven't had much time to pour through my number theory book. I'm wondering what the notation for writing an integer as its digits is. 
For example, given $435$ is it something like $4|3|5$?
Thanks 
 A: I think you're looking for something like $\overline{ABCD}$ as a shorthand for $1000A+100B+10C+D$. I see this notation used sometimes in problems dealing with a number's digits.
A: I always used 
$$[a,b,c,\dots,z]_B$$
where $a,b,c,\dots,z$ are base-$10$ numbersto represent a number in base $B$. The advantage is that $a,b,c, \dots$ don't have to be single-digit integers.
For example, $[10, 9, 8]_{16} = 10\cdot 16^2 + 9 \cdot 16 + 8$. If it is clear what I'm doing, I don't use the brackets when doing arithmetic in base $B$.
For example, to compute $3 \times [10, 9, 8]_{16}$:
\begin{array}{c}
         & 10 &  9 &  8 \\
  \times &    &    &  3 \\
      -- & -- & -- & -- \\
         & 30 & 27 & 24 \\
\end{array}
and $[30, 27, 24]_{16} = [30, 28, 8]_{16} = [31, 12, 8]_{16} = [15, 1, 12, 8]_{16}$.
A: If you want to do something, just do it.
Say:  For purpose of notation am going to indicate a number use expression seperated by $|$ to mean an integer whose digits are the values between bars.  What I mean for example $|a|9-a|2$ will mean a three digit number where the first digit is $a$, the second $9-a$, and the third digit is $2$.  i.e. $a|9-a|2 = a*10^2 + (9-a)*10 + 2$.
It doesn't matter if there is or isn't any standard notation (there isn't).  You have expressed what you intend.
