The number 28987
28987 is a composite number with 8 divisors. Its prime factorisation is 7 × 41 × 101. Divisors (8): 1, 7, 41, 101, 287, 707, 4141, 28987.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 28987: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
28987 is composite. Its prime factorisation is
- 3
The divisors add up to 34272; without 28987 itself that is 5285, so 28987 is deficient (5285 is less than 28987). Euler's totient φ(28987) = 24000 numbers up to 28987 share no factor with it.
- 4
The digits of 28987 add up to 34, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 121 steps to reach 1.
LaTeX source of the formulas on this page
\[ 28987 = 7 \times 41 \times 101 \]
28987 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 34272 |
| Euler totient φ(n) | 24000 |
| Square | 840246169 |
| Cube | 24356215700803 |
| Square root | 170.255690 |
| Digit sum / digital root | 34 / 7 |
| Collatz steps to 1 | 121 |
| Scientific notation | 2.8987 × |
28987 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand nine hundred and eighty-seven |
| Binary (base 2) | 111000100111011 |
| Octal (base 8) | 70473 |
| Hexadecimal (base 16) | 713B |
| Base 3 | 1110202121 |
| As time | 28987 seconds = 8 h 3 min 7 s |
Is 28987 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 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | 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 | Yes (28987 ÷ 7 = 4141) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 7) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 28987 a prime number?
No. 28987 = 7 × 41 × 101, so it is divisible by 7.
What are the factors of 28987?
1, 7, 41, 101, 287, 707, 4141, 28987.
What is 28987 in binary?
111000100111011 (hexadecimal 713B, octal 70473).
What is the square root of 28987?
About 170.2557.
Is 28987 divisible by 3?
No. Its digits add up to 34, which is not a multiple of 3.
What is special about the number 28987?
28987 is a happy number: repeatedly adding the squares of its digits reaches 1.