21,491 in words
21,491
twenty-one thousand four hundred ninety-one
21,491 is written twenty-one thousand four hundred ninety-one.
Ways to write it
- As an ordinal
- twenty-one thousand four hundred ninety-first
- Expanded form
- 20,000 + 1,000 + 400 + 90 + 1
Place value
| Place | Digit | Value |
|---|---|---|
| ten thousands | 2 | 20,000 |
| thousands | 1 | 1,000 |
| hundreds | 4 | 400 |
| tens | 9 | 90 |
| ones | 1 | 1 |
Number facts
- Even or odd
- Odd
- Prime or composite
- Prime
- Factors
- 1 and 21,491 (2 factors)
- First 10 multiples
- 21,491, 42,982, 64,473, 85,964, 107,455, 128,946, 150,437, 171,928, 193,419, 214,910
- Square
- 21,491 × 21,491 = 461,863,081
- Square root
- ≈ 146.60
- Sum of the digits
- 2 + 1 + 4 + 9 + 1 = 17
- Rounded to the nearest 10
- 21,490
- Rounded to the nearest 100
- 21,500
- Rounded to the nearest 1000
- 21,000
- Number before
- 21,490
- Number after
- 21,492
- In binary
101001111110011
Quick check
What number comes just after 21,491?
Show the answer
21,492
Is 21,491 even or odd?
Show the answer
Odd
What is 21,491 + 10?
Show the answer
21,501
Practice 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 21,491 in words?
21,491 is written "twenty-one thousand four hundred ninety-one".
Is 21,491 a prime number?
Yes. 21,491 is a prime number: its only factors are 1 and 21,491.
What are the factors of 21,491?
The factors of 21,491 are 1 and 21,491.