Powering 28 LEDs in series by 220VAC - simple stabilizer
Safety is a big issue and testing this directly from 220V AC is a hazard you should avoid. That's the warning done.

Instead of wasting over 3W of heat in a 8.2kohm resistor, use a dropper capacitor before the bridge on the AC side. At 20mA LED current and with 220V ac, 50 Hz I'd estimate a capacitive reactance of about 11k8 ohms would be about right.

\$X_C = \dfrac{1}{2\pi f C}\$

Capacitance will be about 270nF. This should produce a peak current from 220V AC into a load that looks like 60V of 20mA. Here's a simulation: -



Input AC voltage of 50Hz and peak of 311 volts (220VRMS) drives via 270nF capacitor a bridge rectifier. A capacitor is on the output but this can be virtually any value and in fact I've just rechecked and it is not needed. A zener diode of 62 volts rating is simulating the 28 LEDs in series. An insignificant 1 ohm resistor tells me what the current is. The response shows a peak current of about 26mA and an average current of about 13mA.

The circuit linked to in the comments is unsuitable for driving strings of LEDs because of reverse bias diode breakdown problems.

MAKE SURE YOUR 270nF CAPACITOR IS X OR Y RATED AT THE APPROPRIATE SUPPLY VOLTAGE.

The diodes in the bridge I've shown as 1N4007 because I know they are rated easily in excess of the potential voltages that might be present. 500V minimum rating for these diodes I'd say.