Google-sheets – How to convert a numeric value into a time format inside a formula that also contains a string

I wasn't able to reproduce your results. As a matter of fact, it worked perfectly.

What you tried to do is most probably the following:

In A1 you typed in =HYPERLINK(CONCATENATE("http://www.example.com/id/",A1);A1) and this yields an error of coarse.

Update

If you really want to get the result in A1, then you need to use a script.

Code

// global
var ss = SpreadsheetApp.getActiveSpreadsheet();

function onOpen() {
  var menu = [{name: "create URL", functionName: "createURL"}];
  ss.addMenu("URL", menu);
}

function onEdit(e) {
  var activeRange = e.source.getActiveRange();

  if(activeRange.getColumn() == 1) { 
    if(e.value != "") { 
      activeRange.setValue('=HYPERLINK("http://www.example.com/id/'+e.value+'","'+e.value+'")');
    }
  }
}

function createURL() {
  var aCell = ss.getActiveCell(), value = aCell.getValue();
  aCell.setValue('=HYPERLINK("http://www.example.com/id/'+value+'","'+value+'")');  
}

Explained:

The e.value will retrieve the cells value (only applicable a cell). The setValue() will add the concatenated string into the getActiveRange(). All is only executed when e.value contains something and the active range is in column A.

I've created an extra menu option as well, to be able access the script this way.

Example:

I've created an example file for you: onEdit URL builder
Add this script via Tools>Script editor, into the script editor. Press the "bug" button and you can use the script.

Looks as though, as with Excel, the string functions (LEFT, MID, RIGHT) return strings regardless of whether these look like numbers. So a solution is to force conversion with =VALUE hence:

=VALUE(LEFT(A2,FIND("x",A2)-1))  

in ColumnL should provide the input required for the existing =SUMIF formula to function as intended.