21,821 in words
21,821
twenty-one thousand eight hundred and twenty-one
21,821 is written twenty-one thousand eight hundred and twenty-one.
Ways to write it
- As an ordinal
- twenty-one thousand eight hundred and twenty-first
- Expanded form
- 20,000 + 1,000 + 800 + 20 + 1
Place value
| Place | Digit | Value |
|---|---|---|
| ten thousands | 2 | 20,000 |
| thousands | 1 | 1,000 |
| hundreds | 8 | 800 |
| tens | 2 | 20 |
| ones | 1 | 1 |
Number facts
- Even or odd
- Odd
- Prime or composite
- Prime
- Factors
- 1 and 21,821 (2 factors)
- First 10 multiples
- 21,821, 43,642, 65,463, 87,284, 109,105, 130,926, 152,747, 174,568, 196,389, 218,210
- Square
- 21,821 × 21,821 = 476,156,041
- Square root
- ≈ 147.72
- Sum of the digits
- 2 + 1 + 8 + 2 + 1 = 14
- Rounded to the nearest 10
- 21,820
- Rounded to the nearest 100
- 21,800
- Rounded to the nearest 1000
- 22,000
- Number before
- 21,820
- Number after
- 21,822
- In binary
101010100111101
Quick check
What number comes just after 21,821?
Show the answer
21,822
Is 21,821 even or odd?
Show the answer
Odd
What is 21,821 + 10?
Show the answer
21,831
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 21,821 in words?
21,821 is written "twenty-one thousand eight hundred and twenty-one".
Is 21,821 a prime number?
Yes. 21,821 is a prime number: its only factors are 1 and 21,821.
What are the factors of 21,821?
The factors of 21,821 are 1 and 21,821.