The number 20801
20801 is a composite number with 8 divisors. Its prime factorisation is 11 × 31 × 61. Divisors (8): 1, 11, 31, 61, 341, 671, 1891, 20801.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 20801: a Harshad number: divisible by its digit sum 11.
- 2
20801 is composite. Its prime factorisation is
- 3
The divisors add up to 23808; without 20801 itself that is 3007, so 20801 is deficient (3007 is less than 20801). Euler's totient φ(20801) = 18000 numbers up to 20801 share no factor with it.
- 4
The digits of 20801 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 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 20801 = 11 \times 31 \times 61 \]
20801 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 23808 |
| Euler totient φ(n) | 18000 |
| Square | 432681601 |
| Cube | 9000209982401 |
| Square root | 144.225518 |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.0801 × |
20801 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand eight hundred and one |
| Binary (base 2) | 101000101000001 |
| Octal (base 8) | 50501 |
| Hexadecimal (base 16) | 5141 |
| Base 3 | 1001112102 |
| As time | 20801 seconds = 5 h 46 min 41 s |
Is 20801 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 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 1) | 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 | Yes (20801 ÷ 11 = 1891) | 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 20801 a prime number?
No. 20801 = 11 × 31 × 61, so it is divisible by 11.
What are the factors of 20801?
1, 11, 31, 61, 341, 671, 1891, 20801.
What is 20801 in binary?
101000101000001 (hexadecimal 5141, octal 50501).
What is the square root of 20801?
About 144.2255.
Is 20801 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 20801?
20801 is a Harshad number: divisible by its digit sum 11.