Analysis
You got 2 major clues here.
First Clue: 2147483647
What do we know about 2147483647?
From Wikipedia (http://en.wikipedia.org/wiki/2147483647):
The number 2,147,483,647 is also the maximum value for a 32-bit signed integer in computing. It is therefore the maximum value for variables declared as int in many programming languages running on popular computers.
How can we get this number created by the database?
In several ways, all related to INT, but since your "Mobile" field data type is VARCHAR and not INT, as you clearly emphasized, we know that the problem is not in the database itself. If the field was INT, we could have continued exploring the database itself for possible issues. So we eliminate this possibility. This leaves us with possible code issues.
Second Clue: The log
this is getting logged, and shows that the data was correctly entered. But as soon as we go and check in the database very randomly data is incorrect.
Every time the select query is running for the first time after the insert was made and being logged - it shows (in the log) that the data entered was correct and then when you check the db - sometimes it's correct and sometimes it's 2147483647.
The (usual) Suspect
Based on this information, it would be safe to assume that PHP is converting the string to integer somewhere and then put/update this value in the db, after it has already been correctly inserted.
Debugging
There are several good ways to debug this:
1) Search if there is another UPDATE query
that enters data to the Mobile field and overwrites the correct data that was inserted. A full code search of all your files for the term "Mobile" can be a good start.
2) Search for any occurrence of intval
in your code, as this function (or other similar functions/methods) can convert a string to 2147483647: Converting a String to an Integer returns 2147483647
3) Search for any other occurrences of 2147483647 in your MySQL database, just to determine if this is an isolated problem or if anything else get this value and might have this value copied to the Mobile field via some query or another method.
Hope this helps.