8. (10 points) "Low-carbon living" starts now, starts with me. According to calculations, 1 hectare of deciduous broad-leaved forest can absorb 14 tons of carbon dioxide annually. If the cooling temperature of each air conditioner is adjusted from the national recommended $26^{\circ} \mathrm{C}$ to $27^{\circ} \mathrm{C}$, the corresponding annual reduction in carbon dioxide emissions is 21 kilograms. In a certain city, this reduction alone is equivalent to the amount of carbon dioxide absorbed by 25000 hectares of deciduous broad-leaved forest in a year; if each household has 3 air conditioners, the city has approximately $\qquad$ ten thousand households. (Round to the nearest whole number)
【Analysis】First, calculate the weight of carbon dioxide absorbed by 25000 hectares of deciduous broad-leaved forest throughout the year, which is $25000 \times 14=$ 350000 tons, then divide by $3 \times 21$ kilograms, and the problem is solved.

【Solution】Solution: $25000 \times 14=350000$ (tons) $=350000000$ (kilograms)
$$
\begin{array}{l}
350000000 \div(3 \times 21) \\
=350000000 \div 63 \\
\approx 556 \text { (ten thousand households) }
\end{array}
$$

Answer: The city has approximately 556 ten thousand households.
Therefore, the answer is: 556.