The number 21501
21501 is a composite number with 6 divisors. Its prime factorisation is × 2389. Divisors (6): 1, 3, 9, 2389, 7167, 21501.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21501: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.
- 2
21501 is composite. Its prime factorisation is
- 3
The divisors add up to 31070; without 21501 itself that is 9569, so 21501 is deficient (9569 is less than 21501). Euler's totient φ(21501) = 14328 numbers up to 21501 share no factor with it.
- 4
The digits of 21501 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 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21501 = 3^{2} \times 2389 \]21501 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 31070 |
| Euler totient φ(n) | 14328 |
| Square | 462293001 |
| Cube | 9939761814501 |
| Square root | 146.632193 (= 3√2389) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1501 × |
21501 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and one |
| Binary (base 2) | 101001111111101 |
| Octal (base 8) | 51775 |
| Hexadecimal (base 16) | 53FD |
| Base 3 | 1002111100 |
| As time | 21501 seconds = 5 h 58 min 21 s |
Is 21501 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 (21501 ÷ 3 = 7167) | 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 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 | Yes (21501 ÷ 9 = 2389) | 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 7) | 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 21501 a prime number?
No. 21501 = × 2389, so it is divisible by 3.
What are the factors of 21501?
1, 3, 9, 2389, 7167, 21501.
What is 21501 in binary?
101001111111101 (hexadecimal 53FD, octal 51775).
What is the square root of 21501?
About 146.6322, exactly 3√2389.
Is 21501 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 21501?
21501 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.