which capacitor and resistance values ​can I get a 2.1Mhz signal from the tlc555 timer IC?
If you adapt the datasheet high-frequency formulas:

To an astable circuit with output fed back to the capacitor C with a single resistor R (discharge left disconnected), and assume tplh = 225ns, tphl = 110ns and Rout = 200\$\Omega\$ (high) and 28\$\Omega\$ (low) then somewhere around
R= 560\$\Omega\$
C= 100pF
Should give you ~2.1MHz. A simulation yields ~2.8MHz so you would likely need to cut and try. The SPICE model may not be very accurate at high frequencies or they may have made different assumptions.

Note that the maximum frequency is only guaranteed to be 1.2MHz, under somewhat different conditions. The formula also does not account for input capacitance which would tend to decrease the frequency somewhat.
But- the most important thing to note is that at such high frequencies, the frequency is no longer even more-or-less independent of the chip characteristics. In fact, the propagation delays tplh/tphl dominate the frequency calculation rather than R &amp; C. The propagation delays are not tightly specified, and vary with supply voltage and temperature. The output resistance (particularly in the weaker sourcing state) is also a variable factor, though not as important, and it also varies with temperature, supply voltage, etc.
So this is really not a very good way to make a 2.1MHz oscillator.

Edit: Actually building it on a breadboard with a TI TLC555 yields a frequency of 2.04MHz. C was 99pF (measured) and R was 561\$\Omega\$ (measured) . That's about as close as can be expected (equivalent to 110pF including input capacitances and breadboard capacitances). In circuit, with the chip removed it measures 109pF!
And much closer than the SPICE simulation predicted.