Uh, I think you mean antonym.
Anyways, here are some antonyms.
Careless, Certain, Foolish, Inattentive, Incautious
You can list the numbers . keep listing them till you find the same numbers
4251.04
The perimeter (260.8) over 4 is equal to each side length (65.2)
65.2^2 = 4251.04