The number 3981
3981 is a composite number with 4 divisors. Its prime factorisation is 3 × 1327. Divisors (4): 1, 3, 1327, 3981.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 3981: a semiprime: 3 × 1327, the product of two primes.
- 2
3981 is composite. Its prime factorisation is
- 3
The divisors add up to 5312; without 3981 itself that is 1331, so 3981 is deficient (1331 is less than 3981). Euler's totient φ(3981) = 2652 numbers up to 3981 share no factor with it.
- 4
The digits of 3981 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 25 steps to reach 1.
LaTeX source of the formulas on this page
\[ 3981 = 3 \times 1327 \]
3981 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 5312 |
| Euler totient φ(n) | 2652 |
| Square | 15848361 |
| Cube | 63092325141 |
| Square root | 63.095166 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 25 |
| Scientific notation | 3.981 × |
3981 in other forms
| Form | Value |
|---|---|
| In words | three thousand nine hundred and eighty-one |
| Roman numerals | MMMCMLXXXI |
| Binary (base 2) | 111110001101 |
| Octal (base 8) | 7615 |
| Hexadecimal (base 16) | F8D |
| Base 3 | 12110110 |
| As time | 3981 seconds = 1 h 6 min 21 s |
Is 3981 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 (3981 ÷ 3 = 1327) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 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 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 3981 a prime number?
No. 3981 = 3 × 1327, so it is divisible by 3.
What are the factors of 3981?
1, 3, 1327, 3981.
What is 3981 in binary?
111110001101 (hexadecimal F8D, octal 7615).
What is the square root of 3981?
About 63.0952.
What is 3981 in Roman numerals?
MMMCMLXXXI.
Is 3981 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 3981?
3981 is a semiprime: 3 × 1327, the product of two primes.