The number 15665
15665 is a composite number with 8 divisors. Its prime factorisation is 5 × 13 × 241. Divisors (8): 1, 5, 13, 65, 241, 1205, 3133, 15665.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
15665 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
15665 is composite. Its prime factorisation is
- 3
The divisors add up to 20328; without 15665 itself that is 4663, so 15665 is deficient (4663 is less than 15665). Euler's totient φ(15665) = 11520 numbers up to 15665 share no factor with it.
- 4
The digits of 15665 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 58 steps to reach 1.
LaTeX source of the formulas on this page
\[ 15665 = 5 \times 13 \times 241 \]
15665 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 20328 |
| Euler totient φ(n) | 11520 |
| Square | 245392225 |
| Cube | 3844069204625 |
| Square root | 125.159898 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 58 |
| Scientific notation | 1.5665 × |
15665 in other forms
| Form | Value |
|---|---|
| In words | fifteen thousand six hundred and sixty-five |
| Binary (base 2) | 11110100110001 |
| Octal (base 8) | 36461 |
| Hexadecimal (base 16) | 3D31 |
| Base 3 | 210111012 |
| As time | 15665 seconds = 4 h 21 min 5 s |
Is 15665 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 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (15665 ÷ 5 = 3133) | 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 | No (remainder 6) | 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 | No (remainder 5) | 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 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 15665 a prime number?
No. 15665 = 5 × 13 × 241, so it is divisible by 5.
What are the factors of 15665?
1, 5, 13, 65, 241, 1205, 3133, 15665.
What is 15665 in binary?
11110100110001 (hexadecimal 3D31, octal 36461).
What is the square root of 15665?
About 125.1599.
Is 15665 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 15665?
It is a composite number with 8 divisors.