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Half of a A6 paper size is A7. Half of A7 is A8 and so on until A10 - which is the smallest paper size in the ISO 216 system.
According to ISO 216, A1 is 841 mm x 594 mm. This is approx 33.1 inches x 23.4 inches = 774.54 sq inches.
iso 14001 - iso 26000
216 = 216
2163 = 216 x 216 x 216 = 10077696