The number 21525
21525 is a binary palindrome (101010000010101). Its prime factorisation is 3 × × 7 × 41. Divisors (24): 1, 3, 5, 7, 15, 21, 25, 35, 41, 75, 105, 123, 175, 205, 287, 525 … 21525.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21525: a binary palindrome (101010000010101); a Harshad number: divisible by its digit sum 15.
- 2
21525 is composite. Its prime factorisation is
- 3
The divisors add up to 41664; without 21525 itself that is 20139, so 21525 is deficient (20139 is less than 21525). Euler's totient φ(21525) = 9600 numbers up to 21525 share no factor with it.
- 4
The digits of 21525 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21525 = 3 \times 5^{2} \times 7 \times 41 \]21525 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 41664 |
| Euler totient φ(n) | 9600 |
| Square | 463325625 |
| Cube | 9973084078125 |
| Square root | 146.714008 (= 5√861) |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1525 × |
21525 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and twenty-five |
| Binary (base 2) | 101010000010101 |
| Octal (base 8) | 52025 |
| Hexadecimal (base 16) | 5415 |
| Base 3 | 1002112020 |
| As time | 21525 seconds = 5 h 58 min 45 s |
Is 21525 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 (21525 ÷ 3 = 7175) | 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 | Yes (21525 ÷ 5 = 4305) | 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 | Yes (21525 ÷ 7 = 3075) | 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 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 9) | 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 21525 a prime number?
No. 21525 = 3 × × 7 × 41, so it is divisible by 3.
What are the factors of 21525?
1, 3, 5, 7, 15, 21, 25, 35, 41, 75, 105, 123, 175, 205, 287, 525, 615, 861, 1025, 1435, 3075, 4305, 7175, 21525.
What is 21525 in binary?
101010000010101 (hexadecimal 5415, octal 52025).
What is the square root of 21525?
About 146.7140, exactly 5√861.
Is 21525 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 21525?
21525 is a binary palindrome (101010000010101); a Harshad number: divisible by its digit sum 15.