27
27 = 3*3*3 (3 cubed = 27)
2+7 = 9
The square root of 9 is 3.
Find a four digit number whose digits will be reversed when multiplied by nine?
A perfect square.
What is the units digit of the least whole number greater than 1000 whose digits are all different?
its called a "perfect square"
A perfect square.
The number is 81.
4,624 = 682
252 = 625
52 is a number whose digits have a product of 10.
The largest 3 digit number whose digits are all primes is 777. The largest 3 digit number with different prime digits is 753.
Find a four digit number whose digits will be reversed when multiplied by nine?
The largest three digit prime number whose digits are all primes is 773.
I did it by trial and error. 7^2 is 49. 4 + 9 = 13
23
Work it out with a few clues. Only a 3 can be the last digit of number whose square has a 9 at the end. There are 4 digits in the square, so the root is greater than 31, and less than 100. The square of 5 = 25, so the square of 50 = 2500
69
279,999,720