The number 1251
1251 is a composite number with 6 divisors. Its prime factorisation is × 139. Divisors (6): 1, 3, 9, 139, 417, 1251.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1251: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.
- 2
1251 is composite. Its prime factorisation is
- 3
The divisors add up to 1820; without 1251 itself that is 569, so 1251 is deficient (569 is less than 1251). Euler's totient φ(1251) = 828 numbers up to 1251 share no factor with it.
- 4
The digits of 1251 add up to 9, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 26 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1251 = 3^{2} \times 139 \]1251 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 1820 |
| Euler totient φ(n) | 828 |
| Square | 1565001 |
| Cube | 1957816251 |
| Square root | 35.369478 (= 3√139) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 26 |
| Scientific notation | 1.251 × |
1251 in other forms
| Form | Value |
|---|---|
| In words | one thousand two hundred and fifty-one |
| Roman numerals | MCCLI |
| Binary (base 2) | 10011100011 |
| Octal (base 8) | 2343 |
| Hexadecimal (base 16) | 4E3 |
| Base 3 | 1201100 |
| As time | 1251 seconds = 20 min 51 s |
Is 1251 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 (1251 ÷ 3 = 417) | 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 | 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 | Yes (1251 ÷ 9 = 139) | 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 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 1251 a prime number?
No. 1251 = × 139, so it is divisible by 3.
What are the factors of 1251?
1, 3, 9, 139, 417, 1251.
What is 1251 in binary?
10011100011 (hexadecimal 4E3, octal 2343).
What is the square root of 1251?
About 35.3695, exactly 3√139.
What is 1251 in Roman numerals?
MCCLI.
Is 1251 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 1251?
1251 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.