The number 87815
87815 is a composite number with 16 divisors. Its prime factorisation is 5 × 7 × 13 × 193. Divisors (16): 1, 5, 7, 13, 35, 65, 91, 193, 455, 965, 1351, 2509, 6755, 12545, 17563, 87815.
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How to work it out
- 1
What is special about 87815: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
87815 is composite. Its prime factorisation is
- 3
The divisors add up to 130368; without 87815 itself that is 42553, so 87815 is deficient (42553 is less than 87815). Euler's totient φ(87815) = 55296 numbers up to 87815 share no factor with it.
- 4
The digits of 87815 add up to 29, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 151 steps to reach 1.
LaTeX source of the formulas on this page
\[ 87815 = 5 \times 7 \times 13 \times 193 \]
87815 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 130368 |
| Euler totient φ(n) | 55296 |
| Square | 7711474225 |
| Cube | 677183109068375 |
| Square root | 296.335958 |
| Digit sum / digital root | 29 / 2 |
| Collatz steps to 1 | 151 |
| Scientific notation | 8.7815 × |
87815 in other forms
| Form | Value |
|---|---|
| In words | eighty-seven thousand eight hundred and fifteen |
| Binary (base 2) | 10101011100000111 |
| Octal (base 8) | 253407 |
| Hexadecimal (base 16) | 15707 |
| Base 3 | 11110110102 |
| As time | 87815 seconds = 24 h 23 min 35 s |
Is 87815 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 2) | 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 | Yes (87815 ÷ 5 = 17563) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (87815 ÷ 7 = 12545) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 2) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 5) | 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 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 87815 a prime number?
No. 87815 = 5 × 7 × 13 × 193, so it is divisible by 5.
What are the factors of 87815?
1, 5, 7, 13, 35, 65, 91, 193, 455, 965, 1351, 2509, 6755, 12545, 17563, 87815.
What is 87815 in binary?
10101011100000111 (hexadecimal 15707, octal 253407).
What is the square root of 87815?
About 296.3360.
Is 87815 divisible by 3?
No. Its digits add up to 29, which is not a multiple of 3.
What is special about the number 87815?
87815 is a happy number: repeatedly adding the squares of its digits reaches 1.