The number 21722
21722 is a composite number with 4 divisors. Its prime factorisation is 2 × 10861. Divisors (4): 1, 2, 10861, 21722.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21722: a semiprime: 2 × 10861, the product of two primes.
- 2
21722 is composite. Its prime factorisation is
- 3
The divisors add up to 32586; without 21722 itself that is 10864, so 21722 is deficient (10864 is less than 21722). Euler's totient φ(21722) = 10860 numbers up to 21722 share no factor with it.
- 4
The digits of 21722 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 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21722 = 2 \times 10861 \]
21722 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 32586 |
| Euler totient φ(n) | 10860 |
| Square | 471845284 |
| Cube | 10249423259048 |
| Square root | 147.383853 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1722 × |
21722 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and twenty-two |
| Binary (base 2) | 101010011011010 |
| Octal (base 8) | 52332 |
| Hexadecimal (base 16) | 54DA |
| Base 3 | 1002210112 |
| As time | 21722 seconds = 6 h 2 min 2 s |
Is 21722 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21722 ÷ 2 = 10861) | 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 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | 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 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 2) | 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 | No (remainder 2) | 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 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21722 a prime number?
No. 21722 = 2 × 10861, so it is divisible by 2.
What are the factors of 21722?
1, 2, 10861, 21722.
What is 21722 in binary?
101010011011010 (hexadecimal 54DA, octal 52332).
What is the square root of 21722?
About 147.3839.
Is 21722 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 21722?
21722 is a semiprime: 2 × 10861, the product of two primes.