The number 71840
71840 is a composite number with 24 divisors. Its prime factorisation is × 5 × 449. Divisors (24): 1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 160, 449, 898, 1796, 2245 … 71840.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 71840: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 20.
- 2
71840 is composite. Its prime factorisation is
- 3
The divisors add up to 170100; without 71840 itself that is 98260, so 71840 is abundant (98260 is more than 71840). Euler's totient φ(71840) = 28672 numbers up to 71840 share no factor with it.
- 4
The digits of 71840 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 50 steps to reach 1.
LaTeX source of the formulas on this page
\[ 71840 = 2^{5} \times 5 \times 449 \]71840 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 170100 |
| Euler totient φ(n) | 28672 |
| Square | 5160985600 |
| Cube | 370765205504000 |
| Square root | 268.029849 (= 4√4490) |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 50 |
| Scientific notation | 7.184 × |
71840 in other forms
| Form | Value |
|---|---|
| In words | seventy-one thousand eight hundred and forty |
| Binary (base 2) | 10001100010100000 |
| Octal (base 8) | 214240 |
| Hexadecimal (base 16) | 118A0 |
| Base 3 | 10122112202 |
| As time | 71840 seconds = 19 h 57 min 20 s |
Is 71840 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (71840 ÷ 2 = 35920) | 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 | Yes (71840 ÷ 4 = 17960) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (71840 ÷ 5 = 14368) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | 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 | Yes (71840 ÷ 8 = 8980) | 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 | Yes (71840 ÷ 10 = 7184) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 71840 a prime number?
No. 71840 = × 5 × 449, so it is divisible by 2.
What are the factors of 71840?
1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 160, 449, 898, 1796, 2245, 3592, 4490, 7184, 8980, 14368, 17960, 35920, 71840.
What is 71840 in binary?
10001100010100000 (hexadecimal 118A0, octal 214240).
What is the square root of 71840?
About 268.0298, exactly 4√4490.
Is 71840 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 71840?
71840 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 20.