The number 2,147,483,647 is the eighth Mersenne prime, equal to 231 − 1. It is one of only four known double Mersenne primes.And
Euler ascertained that 231 − 1 = 2147483647 is a prime number; and this is the greatest at present known to be such, and, consequently, the last of the above perfect numbers [i.e., 230(231− 1)], which depends upon this, is the greatest perfect number known at present, and probably the greatest that ever will be discovered; for as they are merely curious, without being useful, it is not likely that any person will attempt to find one beyond it.So as you may already guessed, I figured out what was wrong, telephone field in the database was int and limit was 11 digits. The problem is occurred when the telephone number is bigger the 2147483647, basically overflow condition happen here, well in reality we don’t have a telephone number which is bigger than 2147483647.
As I always interested in Mathematics, this caused me to read more about such numbers which made story more fascinating