The number 21973
21973 is a binary palindrome (101010111010101). Its prime factorisation is 7 × 43 × 73. Divisors (8): 1, 7, 43, 73, 301, 511, 3139, 21973.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21973: a binary palindrome (101010111010101).
- 2
21973 is composite. Its prime factorisation is
- 3
The divisors add up to 26048; without 21973 itself that is 4075, so 21973 is deficient (4075 is less than 21973). Euler's totient φ(21973) = 18144 numbers up to 21973 share no factor with it.
- 4
The digits of 21973 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 131 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21973 = 7 \times 43 \times 73 \]
21973 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 26048 |
| Euler totient φ(n) | 18144 |
| Square | 482812729 |
| Cube | 10608844094317 |
| Square root | 148.232925 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.1973 × |
21973 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and seventy-three |
| Binary (base 2) | 101010111010101 |
| Octal (base 8) | 52725 |
| Hexadecimal (base 16) | 55D5 |
| Base 3 | 1010010211 |
| As time | 21973 seconds = 6 h 6 min 13 s |
Is 21973 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 1) | 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 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (21973 ÷ 7 = 3139) | 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 4) | 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 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21973 a prime number?
No. 21973 = 7 × 43 × 73, so it is divisible by 7.
What are the factors of 21973?
1, 7, 43, 73, 301, 511, 3139, 21973.
What is 21973 in binary?
101010111010101 (hexadecimal 55D5, octal 52725).
What is the square root of 21973?
About 148.2329.
Is 21973 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 21973?
21973 is a binary palindrome (101010111010101).