The number 1643
1643 is a composite number with 4 divisors. Its prime factorisation is 31 × 53. Divisors (4): 1, 31, 53, 1643.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1643: a semiprime: 31 × 53, the product of two primes.
- 2
1643 is composite. Its prime factorisation is
- 3
The divisors add up to 1728; without 1643 itself that is 85, so 1643 is deficient (85 is less than 1643). Euler's totient φ(1643) = 1560 numbers up to 1643 share no factor with it.
- 4
The digits of 1643 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 73 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1643 = 31 \times 53 \]
1643 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 1728 |
| Euler totient φ(n) | 1560 |
| Square | 2699449 |
| Cube | 4435194707 |
| Square root | 40.533936 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 73 |
| Scientific notation | 1.643 × |
1643 in other forms
| Form | Value |
|---|---|
| In words | one thousand six hundred and forty-three |
| Roman numerals | MDCXLIII |
| Binary (base 2) | 11001101011 |
| Octal (base 8) | 3153 |
| Hexadecimal (base 16) | 66B |
| Base 3 | 2020212 |
| As time | 1643 seconds = 27 min 23 s |
Is 1643 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 3) | 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 3) | 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 3) | 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 1643 a prime number?
No. 1643 = 31 × 53, so it is divisible by 31.
What are the factors of 1643?
1, 31, 53, 1643.
What is 1643 in binary?
11001101011 (hexadecimal 66B, octal 3153).
What is the square root of 1643?
About 40.5339.
What is 1643 in Roman numerals?
MDCXLIII.
Is 1643 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 1643?
1643 is a semiprime: 31 × 53, the product of two primes.