The number 2981
2981 is a composite number with 4 divisors. Its prime factorisation is 11 × 271. Divisors (4): 1, 11, 271, 2981.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 2981: a semiprime: 11 × 271, the product of two primes.
- 2
2981 is composite. Its prime factorisation is
- 3
The divisors add up to 3264; without 2981 itself that is 283, so 2981 is deficient (283 is less than 2981). Euler's totient φ(2981) = 2700 numbers up to 2981 share no factor with it.
- 4
The digits of 2981 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 92 steps to reach 1.
LaTeX source of the formulas on this page
\[ 2981 = 11 \times 271 \]
2981 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 3264 |
| Euler totient φ(n) | 2700 |
| Square | 8886361 |
| Cube | 26490242141 |
| Square root | 54.598535 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 92 |
| Scientific notation | 2.981 × |
2981 in other forms
| Form | Value |
|---|---|
| In words | two thousand nine hundred and eighty-one |
| Roman numerals | MMCMLXXXI |
| Binary (base 2) | 101110100101 |
| Octal (base 8) | 5645 |
| Hexadecimal (base 16) | BA5 |
| Base 3 | 11002102 |
| As time | 2981 seconds = 49 min 41 s |
Is 2981 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 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | 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 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 2) | 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 | Yes (2981 ÷ 11 = 271) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 2981 a prime number?
No. 2981 = 11 × 271, so it is divisible by 11.
What are the factors of 2981?
1, 11, 271, 2981.
What is 2981 in binary?
101110100101 (hexadecimal BA5, octal 5645).
What is the square root of 2981?
About 54.5985.
What is 2981 in Roman numerals?
MMCMLXXXI.
Is 2981 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 2981?
2981 is a semiprime: 11 × 271, the product of two primes.