The number 21051
21051 is a composite number with 6 divisors. Its prime factorisation is × 2339. Divisors (6): 1, 3, 9, 2339, 7017, 21051.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21051: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.
- 2
21051 is composite. Its prime factorisation is
- 3
The divisors add up to 30420; without 21051 itself that is 9369, so 21051 is deficient (9369 is less than 21051). Euler's totient φ(21051) = 14028 numbers up to 21051 share no factor with it.
- 4
The digits of 21051 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 193 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21051 = 3^{2} \times 2339 \]21051 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 30420 |
| Euler totient φ(n) | 14028 |
| Square | 443144601 |
| Cube | 9328636995651 |
| Square root | 145.089627 (= 3√2339) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 193 |
| Scientific notation | 2.1051 × |
21051 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and fifty-one |
| Binary (base 2) | 101001000111011 |
| Octal (base 8) | 51073 |
| Hexadecimal (base 16) | 523B |
| Base 3 | 1001212200 |
| As time | 21051 seconds = 5 h 50 min 51 s |
Is 21051 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 (21051 ÷ 3 = 7017) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21051 ÷ 9 = 2339) | 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 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21051 a prime number?
No. 21051 = × 2339, so it is divisible by 3.
What are the factors of 21051?
1, 3, 9, 2339, 7017, 21051.
What is 21051 in binary?
101001000111011 (hexadecimal 523B, octal 51073).
What is the square root of 21051?
About 145.0896, exactly 3√2339.
Is 21051 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 21051?
21051 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.