The number 8121
8121 is a composite number with 4 divisors. Its prime factorisation is 3 × 2707. Divisors (4): 1, 3, 2707, 8121.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 8121: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 2707, the product of two primes.
- 2
8121 is composite. Its prime factorisation is
- 3
The divisors add up to 10832; without 8121 itself that is 2711, so 8121 is deficient (2711 is less than 8121). Euler's totient φ(8121) = 5412 numbers up to 8121 share no factor with it.
- 4
The digits of 8121 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 39 steps to reach 1.
LaTeX source of the formulas on this page
\[ 8121 = 3 \times 2707 \]
8121 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 10832 |
| Euler totient φ(n) | 5412 |
| Square | 65950641 |
| Cube | 535585155561 |
| Square root | 90.116591 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 39 |
| Scientific notation | 8.121 × |
8121 in other forms
| Form | Value |
|---|---|
| In words | eight thousand one hundred and twenty-one |
| Binary (base 2) | 1111110111001 |
| Octal (base 8) | 17671 |
| Hexadecimal (base 16) | 1FB9 |
| Base 3 | 102010210 |
| As time | 8121 seconds = 2 h 15 min 21 s |
Is 8121 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 (8121 ÷ 3 = 2707) | 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 3) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | 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 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 8121 a prime number?
No. 8121 = 3 × 2707, so it is divisible by 3.
What are the factors of 8121?
1, 3, 2707, 8121.
What is 8121 in binary?
1111110111001 (hexadecimal 1FB9, octal 17671).
What is the square root of 8121?
About 90.1166.
Is 8121 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 8121?
8121 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 2707, the product of two primes.