[passionpatel]

found the solution

     int number = 0;
     char numberchars[] = "12545555685986589";
     int i = 0;
     int ans = 0;
     int carry = 0;

     char answerArray[100] = {0};

     char remainderArray[100] = {0};
     int remindex = 0;
     int ansindex = 0;
     int remainder = 0;

     while( numberchars[i] != '\0' )
     {
          while( numberchars[i] != '\0' )
          {
               char currentchar[2] = {0};
               currentchar[0]=numberchars[i];

               int num = atoi(currentchar);
               num += remainder;
               remainder = 0;

               if ( num < 2  )
               {               
                    remainder = num;
                    if(i>0)
                         answerArray[ansindex++] = '0';
               }
               else
               {
                    remainder = num % 2;
                    int answer = num / 2;

                    char a[2] = {0};
                    itoa(answer,a,10);

                    answerArray[ansindex++] = a[0];
               }

               i++;
               remainder *= 10;
          }

          char a[2] = {0};
          int rval = remainder / 10;
          itoa(remainder / 10,a,10);
          
          remainderArray[remindex++] = a[0];
          int size = sizeof(answerArray);
          memcpy(numberchars,answerArray,sizeof(answerArray));
           size = sizeof(answerArray);
          memset(answerArray,0,sizeof(answerArray));
          ansindex = 0;
          remainder = 0;
          i=0;
     }

     char int64[8] = {0};

     for(int k=0;remainderArray[k]!= '\0';k++)
     {
          int64[7-(k/8)] |= ((remainderArray[k]-'0') << (k%8));
     }