If the estimated value is very different from the calculated value then the answer is wrong. Unfortunately, it does not work the other way. An estimate can be close to the calculated value but the answer can still be wrong.
How about 3*7*11 = 231 as a product of its prime factors
79 x 1 39.5 x 2
6x2x2
How about: 8*9 = 72
As a product of its prime factors: 2*2*41 = 164
You multiply it and your finding space of what it has. The multiplication makes the squared.
As a product of its prime factors: 2*2*19 = 76
How about 3*7*11 = 231 as a product of its prime factors
79 x 1 39.5 x 2
6x2x2
37 x 2
How about: 8*9 = 72
As a product of its prime factors: 2*2*41 = 164
They are: 3*7 = 21 or 1*21 = 21
1 x 38, 2 x 19.
3 times 35 equals 105
As a product of its prime factors: 333*5 = 135