640 in words
640
six hundred and forty
640 is written six hundred and forty.
Ways to write it
- As an ordinal
- six hundred and fortieth
- Roman numeral
- DCXL
- Expanded form
- 600 + 40
Place value
| Place | Digit | Value |
|---|---|---|
| hundreds | 6 | 600 |
| tens | 4 | 40 |
| ones | 0 | 0 |
Number facts
- Even or odd
- Even
- Prime or composite
- Composite
- Factors
- 1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 320 and 640 (16 factors)
- First 10 multiples
- 640, 1,280, 1,920, 2,560, 3,200, 3,840, 4,480, 5,120, 5,760, 6,400
- Square
- 640 × 640 = 409,600
- Square root
- ≈ 25.30
- Sum of the digits
- 6 + 4 + 0 = 10
- Rounded to the nearest 10
- 640
- Rounded to the nearest 100
- 600
- Number before
- 639
- Number after
- 641
- In binary
1010000000
Quick check
What number comes just after 640?
Show the answer
641
Is 640 even or odd?
Show the answer
Even
What is 640 + 10?
Show the answer
650
Practise with a game
Factors, Multiples & Primes
Multiples, factors, prime numbers, square numbers and prime factors.
Roman Numerals
Read and write Roman numerals from I to 3,999.Frequently asked questions
How do you write 640 in words?
640 is written "six hundred and forty".
Is 640 a prime number?
No. 640 is a composite number, because it has more than two factors.
What are the factors of 640?
The factors of 640 are 1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 320 and 640.
How do you write 640 in Roman numerals?
640 in Roman numerals is DCXL.