The number 31989
31989 is a composite number with 4 divisors. Its prime factorisation is 3 × 10663. Divisors (4): 1, 3, 10663, 31989.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31989: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 10663, the product of two primes.
- 2
31989 is composite. Its prime factorisation is
- 3
The divisors add up to 42656; without 31989 itself that is 10667, so 31989 is deficient (10667 is less than 31989). Euler's totient φ(31989) = 21324 numbers up to 31989 share no factor with it.
- 4
The digits of 31989 add up to 30, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 54 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31989 = 3 \times 10663 \]
31989 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 42656 |
| Euler totient φ(n) | 21324 |
| Square | 1023296121 |
| Cube | 32734219614669 |
| Square root | 178.854690 |
| Digit sum / digital root | 30 / 3 |
| Collatz steps to 1 | 54 |
| Scientific notation | 3.1989 × |
31989 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand nine hundred and eighty-nine |
| Binary (base 2) | 111110011110101 |
| Octal (base 8) | 76365 |
| Hexadecimal (base 16) | 7CF5 |
| Base 3 | 1121212210 |
| As time | 31989 seconds = 8 h 53 min 9 s |
Is 31989 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 (31989 ÷ 3 = 10663) | 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 4) | 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 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 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 1) | 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 31989 a prime number?
No. 31989 = 3 × 10663, so it is divisible by 3.
What are the factors of 31989?
1, 3, 10663, 31989.
What is 31989 in binary?
111110011110101 (hexadecimal 7CF5, octal 76365).
What is the square root of 31989?
About 178.8547.
Is 31989 divisible by 3?
Yes. Its digits add up to 30, a multiple of 3.
What is special about the number 31989?
31989 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 10663, the product of two primes.