This may be a Rhodes (or some other E Piano sample), not a synth, running through chorus and phaser. But you can get close with most synths, as long as you have a phaser effect.
Osc: Two oscillators, both pulse wave, between square and medium. The pulse width will require some tweaking to get that E Piano sound. Detune them very slightly from each other. We don’t want noticeable pulsations, we’re just looking to smear the tone a bit.
Filter: Low Pass, 24 dB. Turn the Cutoff down pretty far so it’s a nice warm and round sound. Add a little Res. Modulate with…
Filter Envelope: Very small amount. Sustain at 0, Long Decay and Release. We’re mimicking the subtly brighter attack of an e piano, along with its slow rounding as the note rings out.
Chorus: Slow and subtle.
Phaser: Slow but more obvious. This creates that swirling effect.