The number 21740
21740 is a composite number with 12 divisors. Its prime factorisation is × 5 × 1087. Divisors (12): 1, 2, 4, 5, 10, 20, 1087, 2174, 4348, 5435, 10870, 21740.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21740: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21740 is composite. Its prime factorisation is
- 3
The divisors add up to 45696; without 21740 itself that is 23956, so 21740 is abundant (23956 is more than 21740). Euler's totient φ(21740) = 8688 numbers up to 21740 share no factor with it.
- 4
The digits of 21740 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21740 = 2^{2} \times 5 \times 1087 \]21740 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 45696 |
| Euler totient φ(n) | 8688 |
| Square | 472627600 |
| Cube | 10274924024000 |
| Square root | 147.444905 (= 2√5435) |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.174 × |
21740 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and forty |
| Binary (base 2) | 101010011101100 |
| Octal (base 8) | 52354 |
| Hexadecimal (base 16) | 54EC |
| Base 3 | 1002211012 |
| As time | 21740 seconds = 6 h 2 min 20 s |
Is 21740 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21740 ÷ 2 = 10870) | 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 | Yes (21740 ÷ 4 = 5435) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21740 ÷ 5 = 4348) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21740 ÷ 10 = 2174) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21740 a prime number?
No. 21740 = × 5 × 1087, so it is divisible by 2.
What are the factors of 21740?
1, 2, 4, 5, 10, 20, 1087, 2174, 4348, 5435, 10870, 21740.
What is 21740 in binary?
101010011101100 (hexadecimal 54EC, octal 52354).
What is the square root of 21740?
About 147.4449, exactly 2√5435.
Is 21740 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 21740?
21740 is a happy number: repeatedly adding the squares of its digits reaches 1.