What is the largest number k < 100,000 such that k has an odd number of factors?

Question

so i do not know how to solve this problem and is confused on a method to find odd number of factors. How can I find the odd number of factors for a number that high?

Answer 1

The number is $\lfloor \sqrt{100000}\rfloor^2$. Squares and only squares have odd number of divisors.