using stringstream is a common approach:
#include<sstream>
...
std::ostringstream oss;
unsigned int u = 598106;
oss << u;
printf("char array=%s\n", oss.str().c_str());
Update since C++11 there is std::to_string() method -:
#include<string>
...
unsigned int u = 0xffffffff;
std::string s = std::to_string(u);