The number 21743
21743 is a composite number with 4 divisors. Its prime factorisation is 17 × 1279. Divisors (4): 1, 17, 1279, 21743.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21743: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 17; a semiprime: 17 × 1279, the product of two primes.
- 2
21743 is composite. Its prime factorisation is
- 3
The divisors add up to 23040; without 21743 itself that is 1297, so 21743 is deficient (1297 is less than 21743). Euler's totient φ(21743) = 20448 numbers up to 21743 share no factor with it.
- 4
The digits of 21743 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 180 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21743 = 17 \times 1279 \]
21743 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 23040 |
| Euler totient φ(n) | 20448 |
| Square | 472758049 |
| Cube | 10279178259407 |
| Square root | 147.455078 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 180 |
| Scientific notation | 2.1743 × |
21743 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and forty-three |
| Binary (base 2) | 101010011101111 |
| Octal (base 8) | 52357 |
| Hexadecimal (base 16) | 54EF |
| Base 3 | 1002211022 |
| As time | 21743 seconds = 6 h 2 min 23 s |
Is 21743 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 | No (remainder 2) | 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 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 3) | 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 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21743 a prime number?
No. 21743 = 17 × 1279, so it is divisible by 17.
What are the factors of 21743?
1, 17, 1279, 21743.
What is 21743 in binary?
101010011101111 (hexadecimal 54EF, octal 52357).
What is the square root of 21743?
About 147.4551.
Is 21743 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 21743?
21743 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 17; a semiprime: 17 × 1279, the product of two primes.