√391 = 19.77372
The square root of 391 is 19.77372. Free square root calculator with 10 decimal precision.
√391 = 19.77372. Verified: 19.77372 x 19.77372 ≈ 391.
How This Was Calculated
The square root of a number x is the value that, multiplied by itself, gives x:
sqrt(x) x sqrt(x) = x
The nth root generalizes this: nth root of x = x^(1/n). Square roots of non-perfect squares are irrational numbers with non-repeating decimal expansions.
Quick Reference Table
| Input | Result |
|---|---|
| 386 | 19.646883 |
| 389 | 19.723083 |
| 390 | 19.748418 |
| 392 | 19.79899 |
| 393 | 19.824228 |
| 396 | 19.899749 |
Frequently Asked Questions
What is a square root?
The square root of a number is the value that, when multiplied by itself, equals the original number. For example, the square root of 25 is 5 because 5 x 5 = 25.
What is a perfect square?
A perfect square is a number whose square root is a whole number, like 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, and so on.
Can you take the square root of a negative number?
Not in real numbers. The square root of a negative number is imaginary — for example, sqrt(-9) = 3i, where i is the imaginary unit.
How do I estimate a square root manually?
Find the two perfect squares it sits between. For sqrt(50): 49 (7^2) and 64 (8^2), so the answer is between 7 and 8, closer to 7. Actual: 7.071.
What is the square root of 2?
The square root of 2 is approximately 1.4142135624. It is an irrational number, meaning its decimal expansion never ends or repeats.