Long Multiplication: 21 × 4

Long Multiplication Calculator
Multiplicand (number to be multiplied)
Multiplier (number to multiply by)

What is 21 × 4?

Answer

21 × 4 =
84

21 × 4 and 4 × 21 are the same product — the order of the factors never changes the answer, only the working. Below, 21 is multiplied by 4 in a column, digit by digit.

21 × 4 in a Column

The multiplicand goes on top, the multiplier underneath, both aligned on the right. The multiplier has a single digit, so there is one partial product and the answer goes straight under the line.

 21
× 4
 84
21 × 4 = 84

Step-by-Step Solution

Step 1: Multiply the multiplicand by the last digit of the multiplier, 4: 21 × 4 = 84.

  • 1 × 4 = 4. Write 4.
  • 2 × 4 = 8. Write 8.

21 × 4

=

84

Check It, and What It Is Not

Check by dividing back. Multiplication and division undo each other, so 84 ÷ 4 = 21 must come out exactly, with no remainder.

Fractions are a different calculation. Both factors here are whole numbers; for 2/3 or 2 3/4 use the fraction multiplication calculator, which multiplies numerators and denominators separately.

21 × 4 is a number, not an area. If those are the sides of a room in feet, the answer is 84 square feet — the same arithmetic, a different question, and it is answered by the square footage calculator.

Related Calculations

See Also

Long Multiplication Calculator

This calculator multiplies two whole numbers the way it is done on paper: digit by digit, carrying where the column overflows, then adding the partial products together. For example, it can help you find out what is 21 × 4? (The answer is: 84). Enter the multiplicand (e.g. '21') and the multiplier (e.g. '4') and hit the button. The order of the two numbers does not matter — 21 × 4 and 4 × 21 are the same product — so either number can go on top. Fractions and mixed numbers belong to the fraction multiplication calculator, and the reverse operation is long division.
Recalculate with different values ↑

Products of 21

MultiplicationProduct
11 × 444
12 × 448
13 × 452
14 × 456
15 × 460
16 × 464
17 × 468
18 × 472
19 × 476
20 × 480
21 × 484
22 × 488
23 × 492
24 × 496
25 × 4100
26 × 4104
27 × 4108
28 × 4112
29 × 4116
30 × 4120

FAQ

What is 21 × 4?

21 × 4 = 84

Is 21 × 4 the same as 4 × 21?

Yes. Multiplication is commutative, so both come to 84. Only the working differs: this page multiplies by 4, which gives a single partial product.

How do you check that 21 × 4 = 84?

Divide the product back by one of the factors: 84 ÷ 4 = 21 exactly, with no remainder. Multiplication and division undo each other, which is what makes this check work.

What are the partial products of 21 × 4?

There is only one: the multiplier 4 has a single digit, so 21 × 4 = 84 is written straight under the line, with no addition step.

See Also