It asks for the number that, when raised to the power of 3, equals 21.
What is the Cube Root of 21?
The cube root of 21 is 2.7589241764. Calculate another value or review the exact form, nearby perfect powers, and verification.
Answer
Cube Root∛21 = 2.7589241764
CalculatedNon-perfect cubeIrrational
Exact form∛21
Perfect cubeNo
Number typeIrrational
Verification2.75892417643 ≈ 21
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How the answer is calculated
We solve x3 = 21. The resulting value is x = 2.7589241764.
Verification: 2.75892417643 ≈ 21.
Nearest Perfect cubes
| Position | Base | Value |
|---|---|---|
| Lower or equal | 2 | 8 |
| Upper or equal | 3 | 27 |
Number properties
Is 21 a perfect cube?
No. Its cube root is not a whole number.
Is the cube root rational or irrational?
∛21 is irrational because 21 is not a perfect cube.
Visual guide
Cube Root function graph
See how the result changes as the input moves across positive and negative values. Square roots are shown for non-negative inputs; cube roots continue through negative inputs.
Common questions
Frequently asked questions
The decimal answer is rounded for display; the radical form remains exact.
Yes. Enter any supported number in the calculator above and select Calculate.