Transact SQL :: VARCHAR (MAX) Not Showing Full Data

I created a procedure called 'Longtextprocedure'. The length of this procedure is 650000 characters long. When I was giving the following query - select len(routine_definition) from INFORMATION_SCHEMA.routines where ROUTINE_NAME = 'Longextprocedure'; Length is showing as '4000' characters long. It is not showing the remaining part of the procedure, it is showing upto the 4000 characters of procedure code. But when you execute the procedure(exec 'Longtextprocedure') it is showing the exact result. 

My question is i want to read all the 650000 characters long procedure code{select routine_definition from INFORMATION_SCHEMA.routines where ROUTINE_NAME = 'Longextprocedure'} to a variable which is varchar(max). 

When i am trying to read the whole procedure code it is taking 4000 characters of data into the variable not the whole. Is there a way to read the huge procedure code into the variable?

Code:- 

CREATE PROCEDURE FAKEPROCEDURE @procName VARCHAR(50)   --@procName is 'Longtextprocedure'
AS
BEGIN
DECLARE @routineDefinition VARCHAR(MAX);
DECLARE @replaceToChar VARCHAR(MAX);

[Code] ....

When i am trying to execute the line EXEC(@dupliacteRouteDef), it is showing like there is no procedure defined. This is due to '@dupliacteRouteDef' variable is having 4000 characters of data not the whole data. Is there a way to read whole procedure data into the variable irrespective of the length of the string?