The number 1691
1691 is a composite number with 4 divisors. Its prime factorisation is 19 × 89. Divisors (4): 1, 19, 89, 1691.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1691: a semiprime: 19 × 89, the product of two primes.
- 2
1691 is composite. Its prime factorisation is
- 3
The divisors add up to 1800; without 1691 itself that is 109, so 1691 is deficient (109 is less than 1691). Euler's totient φ(1691) = 1584 numbers up to 1691 share no factor with it.
- 4
The digits of 1691 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 135 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1691 = 19 \times 89 \]
1691 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 1800 |
| Euler totient φ(n) | 1584 |
| Square | 2859481 |
| Cube | 4835382371 |
| Square root | 41.121770 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 135 |
| Scientific notation | 1.691 × |
1691 in other forms
| Form | Value |
|---|---|
| In words | one thousand six hundred and ninety-one |
| Roman numerals | MDCXCI |
| Binary (base 2) | 11010011011 |
| Octal (base 8) | 3233 |
| Hexadecimal (base 16) | 69B |
| Base 3 | 2022122 |
| As time | 1691 seconds = 28 min 11 s |
Is 1691 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 1) | 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 4) | 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 8) | 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 8) | 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 1691 a prime number?
No. 1691 = 19 × 89, so it is divisible by 19.
What are the factors of 1691?
1, 19, 89, 1691.
What is 1691 in binary?
11010011011 (hexadecimal 69B, octal 3233).
What is the square root of 1691?
About 41.1218.
What is 1691 in Roman numerals?
MDCXCI.
Is 1691 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 1691?
1691 is a semiprime: 19 × 89, the product of two primes.