Get the number of digits in an int

You can use stringstream for this as shown below

stringstream ss;
int i = 234567545;
ss << i;
cout << ss.str().size() << endl;

How about division:

int length = 1;
int x = 234567545;
while ( x /= 10 )
   length++;

or use the log10 method from <math.h>.

Note that log10 returns a double, so you'll have to adjust the result.

Nobody seems to have mentioned converting it to a string, and then getting the length. Not the most performant, but it definitely does it in one line of code :)

int num = -123456;
int len = to_string(abs(num)).length();

cout << "LENGTH of " << num << " is " << len << endl;    
// prints "LENGTH of 123456 is 6"

Make a function :

int count_numbers ( int num) {
   int count =0;
   while (num !=0) {   
      count++;  
      num/=10;
   } 
   return count;
}