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20^{20} = 2^{20} \times 2^{20} \times 5^{20} = 2^{40} \times 5^{20}
m^2
2
5
21 \times 11 = 231
20^{20} = 2^{20} \times 2^{20} \times 5^{20} = 2^{40} \times 5^{20}m^2from any number of factors2and5as long as they are even (including 0), therefore the total number of combinations is21 \times 11 = 231.