Which of the following numbers will replace the question mark (?) in the given series?9, 45, 180, ?, 1080, 1080

Let's analyze the dynamic ratios between consecutive terms in the series:$9\times 5=45$$45\times 4=180$$180\times 3=540$$540\times 2=1080$$1080\times 1=1080$ The multiplying factors are in a decreasing sequence: $\times 5,\times 4,\times 3,\times 2,\times 1$.Therefore, the value of the question mark (?) is $180\times 3=540$.