Correct Answer: 47632

Solution : Let's check the options –
First option: 47632; 32 ² = 1024; 1024 is not equal to the number formed by the first three digits.
Second option: 32418; 18 ² = 324; 324 is equal to the number formed by the first three digits.
Third option: 67626; 26 ² = 676; 676 is equal to the number formed by the first three digits.
Fourth option: 84129; 29 ² = 841; 841 is equal to the number formed by the first three digits.

So, the first option is different from the other three options as 1024 is not equal to the number formed by the first three digits. Hence, the first option is correct.