Artist Rachel Hovnanian and her developer husband, Ara, swapped their swanky 820 Fifth Ave. address for a West 12th Street townhouse, reports The Post’s Jennifer Gould Keil. The deal for literary agent Luke Janklow‘s former home closed yesterday. It had been listed at $17.9 million with broker Paula Del Nunzio. The Hovnanians recently sold their uptown abode for just under its $35 million asking price to Ken Griffin, a Chicago financier, after their snooty co- op board rejected Related Cos. president Jeff Blau‘s $31 million bid last May. Janklow is now divorcing his wife, Sweetiepie restaurant founder Julie Janklow. The ex-sweetiepies bought the townhouse for $4.5 million in 2004.