Cube Root of 21
Cube Root Calculator
What is the cube root of 21?
Answer
∛21 ≈
2.7589
Real cube root: the only number whose cube is 21.
≈ — rounded to 4 decimal places. 21 is not the cube of a rational number, so ∛21 is irrational: its decimal expansion never ends and never repeats.
- Prime factors
- 21 = 3 × 7
- Take out of the root
- No prime appears three times, so ∛21 is already in simplest form.
- Between cubes
- 2³ = 8 < 21 < 27 = 3³, so 2 < ∛21 < 3 and ∛21 ≈ 2.7589
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See Also
- Square Root Calculator - Calculate the square root of any number
- Simplify Square Root Calculator - Write any square root in simplest radical form, step by step
- Prime Factorization - Prime Factorization Calculator
- Scientific Calculator with Memory & History - Free Engineering Calculator Online with Memory Function, Operation History, Logarithms & Trigonometry. Similar to ti-83, ti-84, ti-89
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FAQ
What is the cube root of 21?
∛21 ≈ 2.7589
Can ∛21 be simplified?
No: no prime appears three times in 21, so its only cube factor is 1 and ∛21 is already in simplest form. Since 2³ = 8 < 21 < 27 = 3³, ∛21 lies between 2 and 3: ∛21 ≈ 2.7589.
Is ∛21 a rational number?
No: 21 is not the cube of a rational number, and the cube root of a fraction p/q in lowest terms is rational only when p and q are both cubes. So ∛21 is irrational; its decimal never ends and never repeats: ∛21 ≈ 2.7589.
See Also
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- Cube Root of 16 (∛16): Exact Value and Decimal
- Cube Root of 17 (∛17): Exact Value and Decimal
- Cube Root of 17.5 (∛17.5): Exact Value and Decimal
- Cube Root of 18 (∛18): Exact Value and Decimal
- Cube Root of 19 (∛19): Exact Value and Decimal
- Cube Root of 20 (∛20): Exact Value and Decimal
- Cube Root of 20.25 (∛20.25): Exact Value and Decimal
- Cube Root of 22 (∛22): Exact Value and Decimal
- Cube Root of 23 (∛23): Exact Value and Decimal
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- Cube Root of 25 (∛25): Exact Value and Decimal
- Cube Root of 26 (∛26): Exact Value and Decimal
- Cube Root of 27 (∛27): Exact Value and Decimal
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