What number multiplied by itself equals 21?

Here we will answer: What number multiplied by itself gives 21? In other words, what number times itself will equal 21?

We have identified many different ways of getting the answer to this question:

Algebra Method:
Make an algebra equation and solve for x:

x • x = 21
x ≈ 4.583

Square Root Method:
Take the square root of 21 to get the answer:

√21 ≈ 4.583

Exponent Method:
Make the base 21 and the exponent 0.5 to get the answer:

21^0.5 ≈ 4.583

There you go! Now you know how to calculate "What number multiplied by itself equals 21?"

The bottom line is that 4.583 times itself equals approximately 21 as illustrated here:

4.583 x 4.583 ≈ 21

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The answer on this page is rounded to the nearest thousandth, if necessary.