View Compilation Error

0_0_32315939_7981.cpp:24:2: error: stray '#' in program
   str[i]=str[i]+21;
  ^
0_0_32315939_7981.cpp: In function 'int main()':
0_0_32315939_7981.cpp:24:3: error: lvalue required as unary '&' operand
   str[i]=str[i]+21;
   ^