1233 = 12² + 33²

990100 = 990² + 100²

can you find an eight digit number with the same property? Even longer numbers?

Generally leading zeros are banned in number problems (except for the number 0 itself) which explains why 000000 is not a solution to this problem.

However, 10100 = 10^2 + 100^2 is an interesting solution, and shows that solutions when the two parts are not of equal digits.