BRASILIA, March 30 (Reuters) - Brazil’s central government reported a primary budget deficit of 21.2 billion reais ($3.7 billion) in February, the Treasury said on Tuesday, less than the 26.5 billion reais shortfall economists in a Reuters poll had forecast. That was also 22% smaller in real terms than the deficit in the same month a year ago, while the primary deficit accumulated in the 12 months through February was 776.8 billion reais, worth 9.9% of gross domestic product, Treasury said.