Same word as painless:

accessible, apparent, basic, child's play, cinch, clear, easily done, effortless, elementary, evident, facile, inconsiderable, light, little, manageable, manifest, mere, no bother, no problem, no sweat, no trouble, not burdensome, nothing to it, obvious, painless, paltry, picnic, piece of cake, plain, plain sailing, pushover, royal, simple, simple as ABC, slight, smooth, snap, straightforward, uncomplicated, undemanding, uninvolved, untroublesome, wieldy, yielding