Refer to the passage below and then answer the question afterwards in the same language as the passage:

Passage: Birkhall (BerkHA; from the Scots Birk Hauch: "Birch River-meadow") is a 53,000 acre (210 km²) estate on Royal Deeside, Aberdeenshire, Scotland. It is located alongside the River Muick to the southwest of Ballater.

Question: How many acres is Birkhall estate?
53,000