The number 10021
10021 is a composite number with 4 divisors. Its prime factorisation is 11 × 911. Divisors (4): 1, 11, 911, 10021.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 10021: a semiprime: 11 × 911, the product of two primes.
- 2
10021 is composite. Its prime factorisation is
- 3
The divisors add up to 10944; without 10021 itself that is 923, so 10021 is deficient (923 is less than 10021). Euler's totient φ(10021) = 9100 numbers up to 10021 share no factor with it.
- 4
The digits of 10021 add up to 4, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 91 steps to reach 1.
LaTeX source of the formulas on this page
\[ 10021 = 11 \times 911 \]
10021 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 10944 |
| Euler totient φ(n) | 9100 |
| Square | 100420441 |
| Cube | 1006313239261 |
| Square root | 100.104945 |
| Digit sum / digital root | 4 / 4 |
| Collatz steps to 1 | 91 |
| Scientific notation | 1.0021 × |
10021 in other forms
| Form | Value |
|---|---|
| In words | ten thousand and twenty-one |
| Binary (base 2) | 10011100100101 |
| Octal (base 8) | 23445 |
| Hexadecimal (base 16) | 2725 |
| Base 3 | 111202011 |
| As time | 10021 seconds = 2 h 47 min 1 s |
Is 10021 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 1) | 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | 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 4) | 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 | Yes (10021 ÷ 11 = 911) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 10021 a prime number?
No. 10021 = 11 × 911, so it is divisible by 11.
What are the factors of 10021?
1, 11, 911, 10021.
What is 10021 in binary?
10011100100101 (hexadecimal 2725, octal 23445).
What is the square root of 10021?
About 100.1049.
Is 10021 divisible by 3?
No. Its digits add up to 4, which is not a multiple of 3.
What is special about the number 10021?
10021 is a semiprime: 11 × 911, the product of two primes.