The number 28121
28121 is a composite number with 4 divisors. Its prime factorisation is 61 × 461. Divisors (4): 1, 61, 461, 28121.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 28121: a semiprime: 61 × 461, the product of two primes.
- 2
28121 is composite. Its prime factorisation is
- 3
The divisors add up to 28644; without 28121 itself that is 523, so 28121 is deficient (523 is less than 28121). Euler's totient φ(28121) = 27600 numbers up to 28121 share no factor with it.
- 4
The digits of 28121 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 152 steps to reach 1.
LaTeX source of the formulas on this page
\[ 28121 = 61 \times 461 \]
28121 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 28644 |
| Euler totient φ(n) | 27600 |
| Square | 790790641 |
| Cube | 22237823615561 |
| Square root | 167.693172 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 152 |
| Scientific notation | 2.8121 × |
28121 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand one hundred and twenty-one |
| Binary (base 2) | 110110111011001 |
| Octal (base 8) | 66731 |
| Hexadecimal (base 16) | 6DD9 |
| Base 3 | 1102120112 |
| As time | 28121 seconds = 7 h 48 min 41 s |
Is 28121 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 2) | 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 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 5) | 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 28121 a prime number?
No. 28121 = 61 × 461, so it is divisible by 61.
What are the factors of 28121?
1, 61, 461, 28121.
What is 28121 in binary?
110110111011001 (hexadecimal 6DD9, octal 66731).
What is the square root of 28121?
About 167.6932.
Is 28121 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 28121?
28121 is a semiprime: 61 × 461, the product of two primes.