user: Question: What is the lowest 2013 population estimate of south africa, which has a percentage greater than 19.8 and a 2011 population greater than 51770561?
Columns: ['Rank', 'Province', 'Population (2011)', 'Percentage', 'Population Estimate (2013)']
Types: ['text', 'text', 'real', 'real', 'real']
Sample row: ['1', 'Gauteng', 12272263.0, 23.7, 12728400.0]
SQL:

assistant: SELECT MIN("Population Estimate (2013)") FROM "Table" WHERE "Percentage" > 19.8 AND "Province" = 'south africa' AND "Population (2011)" > 51770561.0;