Arrange the following numbers in descending order:

84627, 8467, 846720, 84672. Also, identify the smallest and largest number.

Find all the prime numbers between 40 and 60.

Convert 3600 cm² into m².

Estimate the following by rounding off each number to the nearest 1000:

(a) 8,756 + 5,234

(b) 12,845 - 6,379

Also write the actual answers and compare them with the estimates.