The number 28161
28161 is a composite number with 16 divisors. Its prime factorisation is × 7 × 149. Divisors (16): 1, 3, 7, 9, 21, 27, 63, 149, 189, 447, 1043, 1341, 3129, 4023, 9387, 28161.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
28161 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
28161 is composite. Its prime factorisation is
- 3
The divisors add up to 48000; without 28161 itself that is 19839, so 28161 is deficient (19839 is less than 28161). Euler's totient φ(28161) = 15984 numbers up to 28161 share no factor with it.
- 4
The digits of 28161 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 108 steps to reach 1.
LaTeX source of the formulas on this page
\[ 28161 = 3^{3} \times 7 \times 149 \]28161 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 48000 |
| Euler totient φ(n) | 15984 |
| Square | 793041921 |
| Cube | 22332853537281 |
| Square root | 167.812395 (= 3√3129) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 108 |
| Scientific notation | 2.8161 × |
28161 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand one hundred and sixty-one |
| Binary (base 2) | 110111000000001 |
| Octal (base 8) | 67001 |
| Hexadecimal (base 16) | 6E01 |
| Base 3 | 1102122000 |
| As time | 28161 seconds = 7 h 49 min 21 s |
Is 28161 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 (28161 ÷ 3 = 9387) | 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 | Yes (28161 ÷ 7 = 4023) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (28161 ÷ 9 = 3129) | 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 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 28161 a prime number?
No. 28161 = × 7 × 149, so it is divisible by 3.
What are the factors of 28161?
1, 3, 7, 9, 21, 27, 63, 149, 189, 447, 1043, 1341, 3129, 4023, 9387, 28161.
What is 28161 in binary?
110111000000001 (hexadecimal 6E01, octal 67001).
What is the square root of 28161?
About 167.8124, exactly 3√3129.
Is 28161 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 28161?
It is a composite number with 16 divisors.