The square root of 2026 is about 45.01111, and it isn't a whole number.
The nearest perfect squares are 45² = 2025 and 46² = 2116, so the root falls just above 45. Since 2026 is only one more than 2025, a quick approximation works well: √(2025 + 1) ≈ 45 + 1/(2 × 45) = 45.01111. The correction for the next term is far below the fifth decimal place, so 45.01111 is accurate to that precision.
If you need more digits for a calculation, a spreadsheet's SQRT function or a calculator will give them, and anyone who wants to check the arithmetic by hand can use the same method on any number near a perfect square.