The number 1261
1261 is a composite number with 4 divisors. Its prime factorisation is 13 × 97. Divisors (4): 1, 13, 97, 1261.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1261: a semiprime: 13 × 97, the product of two primes.
- 2
1261 is composite. Its prime factorisation is
- 3
The divisors add up to 1372; without 1261 itself that is 111, so 1261 is deficient (111 is less than 1261). Euler's totient φ(1261) = 1152 numbers up to 1261 share no factor with it.
- 4
The digits of 1261 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 39 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1261 = 13 \times 97 \]
1261 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 1372 |
| Euler totient φ(n) | 1152 |
| Square | 1590121 |
| Cube | 2005142581 |
| Square root | 35.510562 |
| Digit sum / digital root | 10 / 1 |
| Collatz steps to 1 | 39 |
| Scientific notation | 1.261 × |
1261 in other forms
| Form | Value |
|---|---|
| In words | one thousand two hundred and sixty-one |
| Roman numerals | MCCLXI |
| Binary (base 2) | 10011101101 |
| Octal (base 8) | 2355 |
| Hexadecimal (base 16) | 4ED |
| Base 3 | 1201201 |
| As time | 1261 seconds = 21 min 1 s |
Is 1261 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 1) | 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 5) | 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 7) | 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 1261 a prime number?
No. 1261 = 13 × 97, so it is divisible by 13.
What are the factors of 1261?
1, 13, 97, 1261.
What is 1261 in binary?
10011101101 (hexadecimal 4ED, octal 2355).
What is the square root of 1261?
About 35.5106.
What is 1261 in Roman numerals?
MCCLXI.
Is 1261 divisible by 3?
No. Its digits add up to 10, which is not a multiple of 3.
What is special about the number 1261?
1261 is a semiprime: 13 × 97, the product of two primes.