The number 21431
21431 is a composite number with 4 divisors. Its prime factorisation is 29 × 739. Divisors (4): 1, 29, 739, 21431.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21431: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 29 × 739, the product of two primes.
- 2
21431 is composite. Its prime factorisation is
- 3
The divisors add up to 22200; without 21431 itself that is 769, so 21431 is deficient (769 is less than 21431). Euler's totient φ(21431) = 20664 numbers up to 21431 share no factor with it.
- 4
The digits of 21431 add up to 11, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 193 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21431 = 29 \times 739 \]
21431 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 22200 |
| Euler totient φ(n) | 20664 |
| Square | 459287761 |
| Cube | 9842996005991 |
| Square root | 146.393306 |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 193 |
| Scientific notation | 2.1431 × |
21431 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand four hundred and thirty-one |
| Binary (base 2) | 101001110110111 |
| Octal (base 8) | 51667 |
| Hexadecimal (base 16) | 53B7 |
| Base 3 | 1002101202 |
| As time | 21431 seconds = 5 h 57 min 11 s |
Is 21431 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 1) | 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 4) | 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 2) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | 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 21431 a prime number?
No. 21431 = 29 × 739, so it is divisible by 29.
What are the factors of 21431?
1, 29, 739, 21431.
What is 21431 in binary?
101001110110111 (hexadecimal 53B7, octal 51667).
What is the square root of 21431?
About 146.3933.
Is 21431 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 21431?
21431 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 29 × 739, the product of two primes.