The number 42021
42021 is a binary palindrome (1010010000100101). Its prime factorisation is × 7 × 23 × 29. Divisors (24): 1, 3, 7, 9, 21, 23, 29, 63, 69, 87, 161, 203, 207, 261, 483, 609 … 42021.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 42021: a binary palindrome (1010010000100101); a Harshad number: divisible by its digit sum 9.
- 2
42021 is composite. Its prime factorisation is
- 3
The divisors add up to 74880; without 42021 itself that is 32859, so 42021 is deficient (32859 is less than 42021). Euler's totient φ(42021) = 22176 numbers up to 42021 share no factor with it.
- 4
The digits of 42021 add up to 9, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 150 steps to reach 1.
LaTeX source of the formulas on this page
\[ 42021 = 3^{2} \times 7 \times 23 \times 29 \]42021 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 74880 |
| Euler totient φ(n) | 22176 |
| Square | 1765764441 |
| Cube | 74199187575261 |
| Square root | 204.990244 (= 3√4669) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 150 |
| Scientific notation | 4.2021 × |
42021 in other forms
| Form | Value |
|---|---|
| In words | forty-two thousand and twenty-one |
| Binary (base 2) | 1010010000100101 |
| Octal (base 8) | 122045 |
| Hexadecimal (base 16) | A425 |
| Base 3 | 2010122100 |
| As time | 42021 seconds = 11 h 40 min 21 s |
Is 42021 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 (42021 ÷ 3 = 14007) | 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 1) | 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 | Yes (42021 ÷ 7 = 6003) | 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 | Yes (42021 ÷ 9 = 4669) | 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 1) | 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 42021 a prime number?
No. 42021 = × 7 × 23 × 29, so it is divisible by 3.
What are the factors of 42021?
1, 3, 7, 9, 21, 23, 29, 63, 69, 87, 161, 203, 207, 261, 483, 609, 667, 1449, 1827, 2001, 4669, 6003, 14007, 42021.
What is 42021 in binary?
1010010000100101 (hexadecimal A425, octal 122045).
What is the square root of 42021?
About 204.9902, exactly 3√4669.
Is 42021 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 42021?
42021 is a binary palindrome (1010010000100101); a Harshad number: divisible by its digit sum 9.