How can I access particular memory address during a GDB session?

This is the disassembly of a very simple C program (strcpy() a constant string and print it):

No symbol table is loaded.  Use the "file" command.
Reading symbols from string...done.
(gdb) break 6
Breakpoint 1 at 0x6b8: file string.c, line 6.
(gdb) break 7
Breakpoint 2 at 0x6f2: file string.c, line 7.
(gdb) r
Starting program: /home/wsllnx/Detached/string

Breakpoint 1, main () at string.c:6
6               strcpy(buf, "Memento Mori\n\tInjected_string");
(gdb) disass main
Dump of assembler code for function main:
0x00005555554006b0 <+0>:     push   %rbp
0x00005555554006b1 <+1>:     mov    %rsp,%rbp
0x00005555554006b4 <+4>:     sub    $0x70,%rsp
0x00005555554006b8 <+8>:     lea    -0x70(%rbp),%rax
0x00005555554006bc <+12>:    movabs $0x206f746e656d654d,%rdx
0x00005555554006c6 <+22>:    mov    %rdx,(%rax)
0x00005555554006c9 <+25>:    movabs $0x6e49090a69726f4d,%rcx
0x00005555554006d3 <+35>:    mov    %rcx,0x8(%rax)
0x00005555554006d7 <+39>:    movabs $0x735f64657463656a,%rsi
0x00005555554006e1 <+49>:    mov    %rsi,0x10(%rax)
0x00005555554006e5 <+53>:    movl   $0x6e697274,0x18(%rax)
0x00005555554006ec <+60>:    movw   $0x67,0x1c(%rax)
0x00005555554006f2 <+66>:    lea    -0x70(%rbp),%rax
0x00005555554006f6 <+70>:    mov    %rax,%rdi
0x00005555554006f9 <+73>:    mov    $0x0,%eax
0x00005555554006fe <+78>:    callq  0x555555400560 <printf@plt>
0x0000555555400703 <+83>:    mov    $0x0,%eax
0x0000555555400708 <+88>:    leaveq
0x0000555555400709 <+89>:    retq
End of assembler dump.
(gdb)

I am currently learning how to fully use GBD and I was wondering:

• How can I access particular address like '0x206f746e656d654d'? When I try to do so with x/x or x/s GDB says:

   '0x206f746e656d654d:     Cannot access memory at address 0x206f746e656d654d'
  

Same goes for 0x6e49090a69726f4d, 0x735f64657463656a and so on...

Thanks in advance to all the useful answers.