The number 87381
87381 is a binary palindrome (10101010101010101). Its prime factorisation is × 7 × 19 × 73. Divisors (24): 1, 3, 7, 9, 19, 21, 57, 63, 73, 133, 171, 219, 399, 511, 657, 1197 … 87381.
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How to work it out
- 1
What is special about 87381: a binary palindrome (10101010101010101).
- 2
87381 is composite. Its prime factorisation is
- 3
The divisors add up to 153920; without 87381 itself that is 66539, so 87381 is deficient (66539 is less than 87381). Euler's totient φ(87381) = 46656 numbers up to 87381 share no factor with it.
- 4
The digits of 87381 add up to 27, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 19 steps to reach 1.
LaTeX source of the formulas on this page
\[ 87381 = 3^{2} \times 7 \times 19 \times 73 \]87381 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 153920 |
| Euler totient φ(n) | 46656 |
| Square | 7635439161 |
| Cube | 667192309327341 |
| Square root | 295.602774 (= 3√9709) |
| Digit sum / digital root | 27 / 9 |
| Collatz steps to 1 | 19 |
| Scientific notation | 8.7381 × |
87381 in other forms
| Form | Value |
|---|---|
| In words | eighty-seven thousand three hundred and eighty-one |
| Binary (base 2) | 10101010101010101 |
| Octal (base 8) | 252525 |
| Hexadecimal (base 16) | 15555 |
| Base 3 | 11102212100 |
| As time | 87381 seconds = 24 h 16 min 21 s |
Is 87381 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 (87381 ÷ 3 = 29127) | 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 (87381 ÷ 7 = 12483) | 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 | Yes (87381 ÷ 9 = 9709) | 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 8) | 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 87381 a prime number?
No. 87381 = × 7 × 19 × 73, so it is divisible by 3.
What are the factors of 87381?
1, 3, 7, 9, 19, 21, 57, 63, 73, 133, 171, 219, 399, 511, 657, 1197, 1387, 1533, 4161, 4599, 9709, 12483, 29127, 87381.
What is 87381 in binary?
10101010101010101 (hexadecimal 15555, octal 252525).
What is the square root of 87381?
About 295.6028, exactly 3√9709.
Is 87381 divisible by 3?
Yes. Its digits add up to 27, a multiple of 3.
What is special about the number 87381?
87381 is a binary palindrome (10101010101010101).