This 51st-floor residence spans more than 10,300 square feet — and its prospective owner can be in some deep-pocketed company.

Ken Seiff, a venture capitalist and founder of Blockchange Ventures, is putting his Florida oceanfront sanctuary at Arte Surfside on the market for $12.9 million, The Post has learned.

Giacona had been coming to the Rockaways for years to surf with friends, and he started wondering why he didn’t just live ...