The number 6440
6440 is a composite number with 32 divisors. Its prime factorisation is × 5 × 7 × 23. Divisors (32): 1, 2, 4, 5, 7, 8, 10, 14, 20, 23, 28, 35, 40, 46, 56, 70 … 6440.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 6440: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 14.
- 2
6440 is composite. Its prime factorisation is
- 3
The divisors add up to 17280; without 6440 itself that is 10840, so 6440 is abundant (10840 is more than 6440). Euler's totient φ(6440) = 2112 numbers up to 6440 share no factor with it.
- 4
The digits of 6440 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 23 steps to reach 1.
LaTeX source of the formulas on this page
\[ 6440 = 2^{3} \times 5 \times 7 \times 23 \]6440 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 32 |
| Sum of divisors | 17280 |
| Euler totient φ(n) | 2112 |
| Square | 41473600 |
| Cube | 267089984000 |
| Square root | 80.249611 (= 2√1610) |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 23 |
| Scientific notation | 6.44 × |
6440 in other forms
| Form | Value |
|---|---|
| In words | six thousand four hundred and forty |
| Binary (base 2) | 1100100101000 |
| Octal (base 8) | 14450 |
| Hexadecimal (base 16) | 1928 |
| Base 3 | 22211112 |
| As time | 6440 seconds = 1 h 47 min 20 s |
Is 6440 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (6440 ÷ 2 = 3220) | 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 (6440 ÷ 4 = 1610) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (6440 ÷ 5 = 1288) | 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 | Yes (6440 ÷ 7 = 920) | 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 (6440 ÷ 8 = 805) | 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 | Yes (6440 ÷ 10 = 644) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 5) | 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 6440 a prime number?
No. 6440 = × 5 × 7 × 23, so it is divisible by 2.
What are the factors of 6440?
1, 2, 4, 5, 7, 8, 10, 14, 20, 23, 28, 35, 40, 46, 56, 70, 92, 115, 140, 161, 184, 230, 280, 322, 460, 644, 805, 920, 1288, 1610, 3220, 6440.
What is 6440 in binary?
1100100101000 (hexadecimal 1928, octal 14450).
What is the square root of 6440?
About 80.2496, exactly 2√1610.
Is 6440 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 6440?
6440 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 14.