The number 1801
1801 is the 279th prime number. Its only divisors are 1 and 1801.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1801: the 279th prime number.
- 2
1801 is prime, so its only factors are 1 and 1801. It is the 279th prime; the next prime is 1811 and the one before is 1789.
- 3
The divisors add up to 1802; without 1801 itself that is 1, so 1801 is deficient (1 is less than 1801). Euler's totient φ(1801) = 1800 numbers up to 1801 share no factor with it.
- 4
The digits of 1801 add up to 10, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 161 steps to reach 1.
1801 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 1802 |
| Euler totient φ(n) | 1800 |
| Square | 3243601 |
| Cube | 5841725401 |
| Square root | 42.438190 |
| Digit sum / digital root | 10 / 1 |
| Collatz steps to 1 | 161 |
| Scientific notation | 1.801 × |
1801 in other forms
| Form | Value |
|---|---|
| In words | one thousand eight hundred and one |
| Roman numerals | MDCCCI |
| Binary (base 2) | 11100001001 |
| Octal (base 8) | 3411 |
| Hexadecimal (base 16) | 709 |
| Base 3 | 2110201 |
| As time | 1801 seconds = 30 min 1 s |
Is 1801 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 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | 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 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 1801 a prime number?
Yes. 1801 is divisible only by 1 and itself.
What are the factors of 1801?
1, 1801.
What is 1801 in binary?
11100001001 (hexadecimal 709, octal 3411).
What is the square root of 1801?
About 42.4382.
What is 1801 in Roman numerals?
MDCCCI.
Is 1801 divisible by 3?
No. Its digits add up to 10, which is not a multiple of 3.
What is special about the number 1801?
1801 is the 279th prime number.