The number 2991
2991 is a composite number with 4 divisors. Its prime factorisation is 3 × 997. Divisors (4): 1, 3, 997, 2991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 2991: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 997, the product of two primes.
- 2
2991 is composite. Its prime factorisation is
- 3
The divisors add up to 3992; without 2991 itself that is 1001, so 2991 is deficient (1001 is less than 2991). Euler's totient φ(2991) = 1992 numbers up to 2991 share no factor with it.
- 4
The digits of 2991 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 48 steps to reach 1.
LaTeX source of the formulas on this page
\[ 2991 = 3 \times 997 \]
2991 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 3992 |
| Euler totient φ(n) | 1992 |
| Square | 8946081 |
| Cube | 26757728271 |
| Square root | 54.690036 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 48 |
| Scientific notation | 2.991 × |
2991 in other forms
| Form | Value |
|---|---|
| In words | two thousand nine hundred and ninety-one |
| Roman numerals | MMCMXCI |
| Binary (base 2) | 101110101111 |
| Octal (base 8) | 5657 |
| Hexadecimal (base 16) | BAF |
| Base 3 | 11002210 |
| As time | 2991 seconds = 49 min 51 s |
Is 2991 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (2991 ÷ 3 = 997) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7. |
| 8 | No (remainder 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 2991 a prime number?
No. 2991 = 3 × 997, so it is divisible by 3.
What are the factors of 2991?
1, 3, 997, 2991.
What is 2991 in binary?
101110101111 (hexadecimal BAF, octal 5657).
What is the square root of 2991?
About 54.6900.
What is 2991 in Roman numerals?
MMCMXCI.
Is 2991 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 2991?
2991 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 997, the product of two primes.