The number 21047
21047 is a composite number with 4 divisors. Its prime factorisation is 13 × 1619. Divisors (4): 1, 13, 1619, 21047.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21047: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 13 × 1619, the product of two primes.
- 2
21047 is composite. Its prime factorisation is
- 3
The divisors add up to 22680; without 21047 itself that is 1633, so 21047 is deficient (1633 is less than 21047). Euler's totient φ(21047) = 19416 numbers up to 21047 share no factor with it.
- 4
The digits of 21047 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 180 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21047 = 13 \times 1619 \]
21047 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 22680 |
| Euler totient φ(n) | 19416 |
| Square | 442976209 |
| Cube | 9323320270823 |
| Square root | 145.075842 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 180 |
| Scientific notation | 2.1047 × |
21047 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and forty-seven |
| Binary (base 2) | 101001000110111 |
| Octal (base 8) | 51067 |
| Hexadecimal (base 16) | 5237 |
| Base 3 | 1001212112 |
| As time | 21047 seconds = 5 h 50 min 47 s |
Is 21047 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 2) | 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 5) | 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 5) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 7) | 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 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21047 a prime number?
No. 21047 = 13 × 1619, so it is divisible by 13.
What are the factors of 21047?
1, 13, 1619, 21047.
What is 21047 in binary?
101001000110111 (hexadecimal 5237, octal 51067).
What is the square root of 21047?
About 145.0758.
Is 21047 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 21047?
21047 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 13 × 1619, the product of two primes.