The number 20989
20989 is a composite number with 4 divisors. Its prime factorisation is 139 × 151. Divisors (4): 1, 139, 151, 20989.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 20989: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 139 × 151, the product of two primes.
- 2
20989 is composite. Its prime factorisation is
- 3
The divisors add up to 21280; without 20989 itself that is 291, so 20989 is deficient (291 is less than 20989). Euler's totient φ(20989) = 20700 numbers up to 20989 share no factor with it.
- 4
The digits of 20989 add up to 28, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 87 steps to reach 1.
LaTeX source of the formulas on this page
\[ 20989 = 139 \times 151 \]
20989 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 21280 |
| Euler totient φ(n) | 20700 |
| Square | 440538121 |
| Cube | 9246454621669 |
| Square root | 144.875809 |
| Digit sum / digital root | 28 / 1 |
| Collatz steps to 1 | 87 |
| Scientific notation | 2.0989 × |
20989 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand nine hundred and eighty-nine |
| Binary (base 2) | 101000111111101 |
| Octal (base 8) | 50775 |
| Hexadecimal (base 16) | 51FD |
| Base 3 | 1001210101 |
| As time | 20989 seconds = 5 h 49 min 49 s |
Is 20989 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 1) | 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 1) | 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 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 20989 a prime number?
No. 20989 = 139 × 151, so it is divisible by 139.
What are the factors of 20989?
1, 139, 151, 20989.
What is 20989 in binary?
101000111111101 (hexadecimal 51FD, octal 50775).
What is the square root of 20989?
About 144.8758.
Is 20989 divisible by 3?
No. Its digits add up to 28, which is not a multiple of 3.
What is special about the number 20989?
20989 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 139 × 151, the product of two primes.