The number 15921
15921 is a composite number with 12 divisors. Its prime factorisation is × 29 × 61. Divisors (12): 1, 3, 9, 29, 61, 87, 183, 261, 549, 1769, 5307, 15921.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
15921 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
15921 is composite. Its prime factorisation is
- 3
The divisors add up to 24180; without 15921 itself that is 8259, so 15921 is deficient (8259 is less than 15921). Euler's totient φ(15921) = 10080 numbers up to 15921 share no factor with it.
- 4
The digits of 15921 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 146 steps to reach 1.
LaTeX source of the formulas on this page
\[ 15921 = 3^{2} \times 29 \times 61 \]15921 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 24180 |
| Euler totient φ(n) | 10080 |
| Square | 253478241 |
| Cube | 4035627074961 |
| Square root | 126.178445 (= 3√1769) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 146 |
| Scientific notation | 1.5921 × |
15921 in other forms
| Form | Value |
|---|---|
| In words | fifteen thousand nine hundred and twenty-one |
| Binary (base 2) | 11111000110001 |
| Octal (base 8) | 37061 |
| Hexadecimal (base 16) | 3E31 |
| Base 3 | 210211200 |
| As time | 15921 seconds = 4 h 25 min 21 s |
Is 15921 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 (15921 ÷ 3 = 5307) | 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 | No (remainder 3) | 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 (15921 ÷ 9 = 1769) | 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 4) | 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 15921 a prime number?
No. 15921 = × 29 × 61, so it is divisible by 3.
What are the factors of 15921?
1, 3, 9, 29, 61, 87, 183, 261, 549, 1769, 5307, 15921.
What is 15921 in binary?
11111000110001 (hexadecimal 3E31, octal 37061).
What is the square root of 15921?
About 126.1784, exactly 3√1769.
Is 15921 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 15921?
It is a composite number with 12 divisors.