991 in words
991
nine hundred ninety-one
991 is written nine hundred ninety-one.
Ways to write it
- As an ordinal
- nine hundred ninety-first
- Roman numeral
- CMXCI
- Expanded form
- 900 + 90 + 1
Place value
| Place | Digit | Value |
|---|---|---|
| hundreds | 9 | 900 |
| tens | 9 | 90 |
| ones | 1 | 1 |
Number facts
- Even or odd
- Odd
- Prime or composite
- Prime
- Factors
- 1 and 991 (2 factors)
- First 10 multiples
- 991, 1,982, 2,973, 3,964, 4,955, 5,946, 6,937, 7,928, 8,919, 9,910
- Square
- 991 × 991 = 982,081
- Square root
- ≈ 31.48
- Sum of the digits
- 9 + 9 + 1 = 19
- Rounded to the nearest 10
- 990
- Rounded to the nearest 100
- 1,000
- Number before
- 990
- Number after
- 992
- In binary
1111011111
Quick check
What number comes just after 991?
Show the answer
992
Is 991 even or odd?
Show the answer
Odd
What is 991 + 10?
Show the answer
1,001
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 991 in words?
991 is written "nine hundred ninety-one".
Is 991 a prime number?
Yes. 991 is a prime number: its only factors are 1 and 991.
What are the factors of 991?
The factors of 991 are 1 and 991.
How do you write 991 in Roman numerals?
991 in Roman numerals is CMXCI.