21,840 in words
21,840
twenty-one thousand eight hundred forty
21,840 is written twenty-one thousand eight hundred forty.
Ways to write it
- As an ordinal
- twenty-one thousand eight hundred fortieth
- Expanded form
- 20,000 + 1,000 + 800 + 40
Place value
| Place | Digit | Value |
|---|---|---|
| ten thousands | 2 | 20,000 |
| thousands | 1 | 1,000 |
| hundreds | 8 | 800 |
| tens | 4 | 40 |
| ones | 0 | 0 |
Number facts
- Even or odd
- Even
- Prime or composite
- Composite
- Factors
- 80 factors: too many to list
- First 10 multiples
- 21,840, 43,680, 65,520, 87,360, 109,200, 131,040, 152,880, 174,720, 196,560, 218,400
- Square
- 21,840 × 21,840 = 476,985,600
- Square root
- ≈ 147.78
- Sum of the digits
- 2 + 1 + 8 + 4 + 0 = 15
- Rounded to the nearest 10
- 21,840
- Rounded to the nearest 100
- 21,800
- Rounded to the nearest 1000
- 22,000
- Number before
- 21,839
- Number after
- 21,841
- In binary
101010101010000
Quick check
What number comes just after 21,840?
Show the answer
21,841
Is 21,840 even or odd?
Show the answer
Even
What is 21,840 + 10?
Show the answer
21,850
Practise with a game
Factors, Multiples & Primes
Multiples, factors, prime numbers, square numbers and prime factors.
Number Patterns
Find the missing number in a sequence.Frequently asked questions
How do you write 21,840 in words?
21,840 is written "twenty-one thousand eight hundred forty".
Is 21,840 a prime number?
No. 21,840 is a composite number, because it has more than two factors.