The number 20421
20421 is a composite number with 6 divisors. Its prime factorisation is × 2269. Divisors (6): 1, 3, 9, 2269, 6807, 20421.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 20421: a Harshad number: divisible by its digit sum 9.
- 2
20421 is composite. Its prime factorisation is
- 3
The divisors add up to 29510; without 20421 itself that is 9089, so 20421 is deficient (9089 is less than 20421). Euler's totient φ(20421) = 13608 numbers up to 20421 share no factor with it.
- 4
The digits of 20421 add up to 9, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 61 steps to reach 1.
LaTeX source of the formulas on this page
\[ 20421 = 3^{2} \times 2269 \]20421 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 29510 |
| Euler totient φ(n) | 13608 |
| Square | 417017241 |
| Cube | 8515909078461 |
| Square root | 142.902064 (= 3√2269) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 61 |
| Scientific notation | 2.0421 × |
20421 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand four hundred and twenty-one |
| Binary (base 2) | 100111111000101 |
| Octal (base 8) | 47705 |
| Hexadecimal (base 16) | 4FC5 |
| Base 3 | 1001000100 |
| As time | 20421 seconds = 5 h 40 min 21 s |
Is 20421 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 (20421 ÷ 3 = 6807) | 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 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (20421 ÷ 9 = 2269) | 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 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 20421 a prime number?
No. 20421 = × 2269, so it is divisible by 3.
What are the factors of 20421?
1, 3, 9, 2269, 6807, 20421.
What is 20421 in binary?
100111111000101 (hexadecimal 4FC5, octal 47705).
What is the square root of 20421?
About 142.9021, exactly 3√2269.
Is 20421 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 20421?
20421 is a Harshad number: divisible by its digit sum 9.