The number 1491
1491 is a composite number with 8 divisors. Its prime factorisation is 3 × 7 × 71. Divisors (8): 1, 3, 7, 21, 71, 213, 497, 1491.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
1491 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
1491 is composite. Its prime factorisation is
- 3
The divisors add up to 2304; without 1491 itself that is 813, so 1491 is deficient (813 is less than 1491). Euler's totient φ(1491) = 840 numbers up to 1491 share no factor with it.
- 4
The digits of 1491 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 91 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1491 = 3 \times 7 \times 71 \]
1491 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 2304 |
| Euler totient φ(n) | 840 |
| Square | 2223081 |
| Cube | 3314613771 |
| Square root | 38.613469 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 91 |
| Scientific notation | 1.491 × |
1491 in other forms
| Form | Value |
|---|---|
| In words | one thousand four hundred and ninety-one |
| Roman numerals | MCDXCI |
| Binary (base 2) | 10111010011 |
| Octal (base 8) | 2723 |
| Hexadecimal (base 16) | 5D3 |
| Base 3 | 2001020 |
| As time | 1491 seconds = 24 min 51 s |
Is 1491 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 (1491 ÷ 3 = 497) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (1491 ÷ 7 = 213) | 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 6) | 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 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 1491 a prime number?
No. 1491 = 3 × 7 × 71, so it is divisible by 3.
What are the factors of 1491?
1, 3, 7, 21, 71, 213, 497, 1491.
What is 1491 in binary?
10111010011 (hexadecimal 5D3, octal 2723).
What is the square root of 1491?
About 38.6135.
What is 1491 in Roman numerals?
MCDXCI.
Is 1491 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 1491?
It is a composite number with 8 divisors.