The number 21993
21993 is a composite number with 4 divisors. Its prime factorisation is 3 × 7331. Divisors (4): 1, 3, 7331, 21993.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21993: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 7331, the product of two primes.
- 2
21993 is composite. Its prime factorisation is
- 3
The divisors add up to 29328; without 21993 itself that is 7335, so 21993 is deficient (7335 is less than 21993). Euler's totient φ(21993) = 14660 numbers up to 21993 share no factor with it.
- 4
The digits of 21993 add up to 24, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21993 = 3 \times 7331 \]
21993 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 29328 |
| Euler totient φ(n) | 14660 |
| Square | 483692049 |
| Cube | 10637839233657 |
| Square root | 148.300371 |
| Digit sum / digital root | 24 / 6 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1993 × |
21993 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and ninety-three |
| Binary (base 2) | 101010111101001 |
| Octal (base 8) | 52751 |
| Hexadecimal (base 16) | 55E9 |
| Base 3 | 1010011120 |
| As time | 21993 seconds = 6 h 6 min 33 s |
Is 21993 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 (21993 ÷ 3 = 7331) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 1) | 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 3) | 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 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21993 a prime number?
No. 21993 = 3 × 7331, so it is divisible by 3.
What are the factors of 21993?
1, 3, 7331, 21993.
What is 21993 in binary?
101010111101001 (hexadecimal 55E9, octal 52751).
What is the square root of 21993?
About 148.3004.
Is 21993 divisible by 3?
Yes. Its digits add up to 24, a multiple of 3.
What is special about the number 21993?
21993 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 7331, the product of two primes.