JavaScript (ES6), 10 bytes

_=>(_+_)*_

Needs to be called with the argument as a String, not a Number.

Usage:

(_=>(_+_)*_)('3')
99

-3 bytes thanks to @Quill's suggestion.

Java 8, 29 26 Bytes

God bless lambda

c->Long.decode(c+""+c)*c;

vim, 11

C<C-r>=<C-r>"<C-r>"*<C-r>"<cr>

crcrcrcrcr...

C       change (delete and enter insert mode) until the end of the line
<C-r>=  insert an expression via the special "expression register"
<C-r>"  insert the contents of the default register (what we just C'd)
<C-r>"  ... again
*       multiplied by
<C-r>"  the input (again)
<cr>    insert the result of this expression

C#, 19 23 bytes

n=>int.Parse(""+n+n)*n;

Without strings, 47 bytes

n=>{int i=1;while(i<=n)i*=10;return(i+1)*n*n;};

Python 2.7, 21 bytes:

lambda f:int(`f`*2)*f

Well, this has to be the shortest Python answer I have ever written in the shortest amount of time ever. It's an anonymous lambda function that can be executed by naming it anything you want and then calling it like a normal function wrapped in print(). For instance, if your input is 12, and the function was named H, this this would be called like print(H(12)).

Try It Online! (Ideone)

Note that this only works for values up and equal to 9223372036854775807 since any higher value and repr() puts a L at the end of the integer. Therefore, for values greater than 9223372036854775807, this 24 byte version would be the one that works:

lambda f:int(str(f)*2)*f

Try This Online! (Ideone)

Pyth, 5 4 bytes

*s+`

Explanation:

    Q    input
   `     representation, basically str(Q)
  +  Q   add Q to its own string form
 s       parse int
*     Q  multiply by input
         print

Test it here.

C, 70 68 54 53 52 44

f(n){return(pow(10,(int)log10(n)+1)*n+n)*n;}

Previous version (48 bytes, no math functions), saved 16 bytes thanks to @LeakyNun, 1 byte thanks to @FryAmTheEggman, 4 bytes thanks to @TobySpeight:

f(n,d,i){for(i=d=n;d;d/=10)i*=10;return(i+n)*n;}

Call f() with one argument, the number, and it returns the corresponding uninteresting number.

Test program

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
    while (*++argv) {
        int n = atoi(*argv);
        printf("%d -> %d\n", n, f(n));
    }
    return 0;
}

Test results:

$ ./84712 1 2 3 4 10 174
1 -> 11
2 -> 44
3 -> 99
4 -> 176
10 -> 10100
174 -> 30306276

Emacs, 17 bytes

(*SPACEC-SPACEC-EM-YSPACEC-YC-Y)C-J

Explanation

• (*SPACE adds (* at point (before the number);
• C-SPACEC-EM-Y Select and copy the number;
• SPACE adds a space character at point (after the number);
• C-YC-Y pastes two times the number at point;
• ) adds ) at the end;
• C-J interprets the line as a LISP expression and prints its result.

Exemple

Cursor represented by a pipe (|)

• |174
• (*SPACE (* |174
• C-SPACEC-EM-Y (* 174|
• SPACE (* 174 |
• C-YC-Y (* 174 174174|
• ) (* 174 174174)|
• C-J

Result

(* 174 174174)
30306276|

Jelly, 4 Bytes

;DḌ×

Try it online

Explanation

;DḌ×    Main link. argument : N

 D      Decimal; Yield the digits of N
;       Concatenate N and its digits
  Ḍ     Convert to integer; We get O
   ×    Multiply O and N

Dyalog APL, 7 bytes

⊢×#⍎⍕,⍕

⍕ string representation

⍕, prepend string representation

#⍎ make into number (in root namespace)

⊢× multiply by original number

Retina, 27 20 bytes

^
$_$*: $_
:
$_$*:
:

Gets a bit slow for large inputs, because before the last the stage the result is represented in unary.

Try it online! (The first line enables a linefeed-separated test suite.)

Explanation

I'll use 2 as an example input (because the unary representations get a bit unwieldy for larger inputs).

Stage 1: Substitution

^
$_$*: $_

By matching the beginning of the string with ^ we simply prepend some stuff. $_ refers to the input string itself and $*: means we insert that many colons. So we get:

:: 22

Stage 2: Substitution

:
$_$*:

Now we match every : and again replace it with $_$*:. Of course, this time $_ doesn't evaluate to an integer (but to :: 22 in our example), but $* just looks for the first decimal in the string, so this evaluates to the input concatenated to itself (O in the challenge specification). We'll end up with N*O colons, followed by O:

:::::::::::::::::::::::::::::::::::::::::::: 22

Stage 3: Match

:

All that's left is counting the :s to convert from unary back to decimal, which is exactly what this stage does.

CJam, 8 bytes

ri_`_+i*

Try it online!

r     e# Read input
i     e# Convert to integer
_     e# Duplicate
`     e# Convert to string
_     e# Duplicate
+     e# Concatenate
i     e# Convert to integer
*     e# Multiply. Implicitly display

Python, 42 bytes

Pure arithmetic approach, without strings!

f=lambda n,m=1:m<=n and f(n,m*10)or-~m*n*n

Ideone it!

Awk, 13 bytes

$0=($0$0)*$0

Set the line to 2 of itself multiplied by itself

Lua, 20 Bytes

Takes in a command-line argument, and outputs via STDIN

a=...print((a..a)*a)

Jelly, 8 6 bytes

ŒṘẋ2v×

Try it online!

Explanation

ŒṘẋ2v× - Main link. Left argument: the number to convert

     × - Multiply
    v  - an evaluation of the left argument
ŒṘ     - converted to string
  ẋ    - multiplied by
   2   - two and the left argument

Matlab / Octave, 20 bytes

@(x)eval([x x 42 x])

This is an anonymous function that takes the input as a string.

Example use:

>> f = @(x)eval([x x 42 x])
f = 
    @(x)eval([x,x,42,x])
>> f('12')
ans =
       14544

Or try it online with ideone.

Explanation

The code builds a string by concatenating the input string twice, then the character * (that has ASCII code 42), then the string again. The concatenated string is then evaluated.

Perl, 11 bytes

$_*=$_ x2

+ the p and l flags.

(run with perl -ple '$_*=$_ x2')

-2 bytes thanks to pipe.

Excel VBA, 35 Bytes

Sub called with number, msgbox returns answer

Sub B(a)
MsgBox (a & a) * a
End Sub

Alternative Excel VBA, 42 Bytes

Number given in formula, returns answer.

Function B(a)
B = (a & a) * a
End Function

MATL, 6 bytes

tVthU*

Try it online!

tV     % Input number implicitly. Duplicate and convert to string
th     % Duplicate and concatenate the two equal strings
U      % Convert to number
*      % Multiply

zsh, 13 bytes

<<<$[$1$1*$1]

Takes input as a command line argument, outputs to STDOUT.

This only works in zsh, but here's 15 bytes in Bash using echo instead of <<<:

echo $[$1$1*$1]

J, 7 bytes

*,~&.":

Explanation

*,~&.":  Input: n
     ":  Format n as a string
 ,~&.    Reflect and join the string to make "nn"
         and parse the string to get a number
*        Multiply that number by n

Brachylog, 7 bytes

:?c:?*.

Explanation

:?c      Concatenate Input to itself
   :?*.  Output is that concatenation times Input

PHP, 25 24 bytes

Short opening tags are useful for surprisingly few golfing challenges, luckily this is one of them. Unfortunately operator precedence is the opposite of the order you need to do them in so lots of brackets are needed.

<?=($a=$argv[1])*"$a$a";

edit: I realised that seeing as how I'm using brackets anyway I can effectively skip the concatenation operator by changing the written order of the operations around.

dc, 11 10 bytes

ddZAr^1+**

I knew that eventually I would find a use for the Z command!

Operation is fairly simple - count the digits, take 10 raised to that power and add one. This gives a multiplier that concatenates the number with itself. Then just multiply.

I/O uses the stack, as usual for dc.

Full program

This is what I used for the tests:

#!/usr/bin/dc
?
ddZAr^1+**
p

The two extra commands give us pipeline I/O.

Tests

$ for i in 1 2 3 10 174; do printf '%d -> ' $i; ./84712.dc <<<$i; done
1 -> 11
2 -> 44
3 -> 99
10 -> 10100
174 -> 30306276

Thanks are due to Sir Biden XVII (1 byte).

Clojure, 22 bytes

#(*(bigint(str % %))%)

Anonymous function which concatenates string representation of its argument covnerts it to BigInteger and multiplies by the argument. The output is in format 11N (N signifies its a bigint), if there should be no N at the end then we can use

#(*(read-string(str % %))%)

for 27 bytes.

See it online: https://ideone.com/QqYfpo

Pyke, 5 4 bytes

`+b*

Try it here!

`    -    str(input)
 +   -   ^+input  (convert to string implicitly)
  b  -  int(^)
   * - ^*input

Also 5 bytes with string inputs

+bRb*
+]mbB

SpecBAS - 30 bytes

1 INPUT n$: ?VAL(n$+n$)*VAL n$

My shortest SpecBAS answer yet :-)

Python, 51 Bytes

from math import*
g=lambda x:x*(x+x*10**(1+int(log10(x))))

Here's the mathematical way to do it (friend of mine found the formula). I guess using it wouldn't produce an answer shorter than 3 bytes. :)