The number 15221
15221 is a composite number with 4 divisors. Its prime factorisation is 31 × 491. Divisors (4): 1, 31, 491, 15221.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 15221: a semiprime: 31 × 491, the product of two primes.
- 2
15221 is composite. Its prime factorisation is
- 3
The divisors add up to 15744; without 15221 itself that is 523, so 15221 is deficient (523 is less than 15221). Euler's totient φ(15221) = 14700 numbers up to 15221 share no factor with it.
- 4
The digits of 15221 add up to 11, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 32 steps to reach 1.
LaTeX source of the formulas on this page
\[ 15221 = 31 \times 491 \]
15221 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 15744 |
| Euler totient φ(n) | 14700 |
| Square | 231678841 |
| Cube | 3526383638861 |
| Square root | 123.373417 |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 32 |
| Scientific notation | 1.5221 × |
15221 in other forms
| Form | Value |
|---|---|
| In words | fifteen thousand two hundred and twenty-one |
| Binary (base 2) | 11101101110101 |
| Octal (base 8) | 35565 |
| Hexadecimal (base 16) | 3B75 |
| Base 3 | 202212202 |
| As time | 15221 seconds = 4 h 13 min 41 s |
Is 15221 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 | No (remainder 1) | 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 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 5) | 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 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 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 15221 a prime number?
No. 15221 = 31 × 491, so it is divisible by 31.
What are the factors of 15221?
1, 31, 491, 15221.
What is 15221 in binary?
11101101110101 (hexadecimal 3B75, octal 35565).
What is the square root of 15221?
About 123.3734.
Is 15221 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 15221?
15221 is a semiprime: 31 × 491, the product of two primes.