The number 21058
21058 is a composite number with 4 divisors. Its prime factorisation is 2 × 10529. Divisors (4): 1, 2, 10529, 21058.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21058: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 2 × 10529, the product of two primes.
- 2
21058 is composite. Its prime factorisation is
- 3
The divisors add up to 31590; without 21058 itself that is 10532, so 21058 is deficient (10532 is less than 21058). Euler's totient φ(21058) = 10528 numbers up to 21058 share no factor with it.
- 4
The digits of 21058 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21058 = 2 \times 10529 \]
21058 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 31590 |
| Euler totient φ(n) | 10528 |
| Square | 443439364 |
| Cube | 9337946127112 |
| Square root | 145.113748 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.1058 × |
21058 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and fifty-eight |
| Binary (base 2) | 101001001000010 |
| Octal (base 8) | 51102 |
| Hexadecimal (base 16) | 5242 |
| Base 3 | 1001212221 |
| As time | 21058 seconds = 5 h 50 min 58 s |
Is 21058 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21058 ÷ 2 = 10529) | 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 2) | 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 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | 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 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | 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 10) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21058 a prime number?
No. 21058 = 2 × 10529, so it is divisible by 2.
What are the factors of 21058?
1, 2, 10529, 21058.
What is 21058 in binary?
101001001000010 (hexadecimal 5242, octal 51102).
What is the square root of 21058?
About 145.1137.
Is 21058 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 21058?
21058 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 2 × 10529, the product of two primes.