The number 21461
21461 is a composite number with 4 divisors. Its prime factorisation is 11 × 1951. Divisors (4): 1, 11, 1951, 21461.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21461: a semiprime: 11 × 1951, the product of two primes.
- 2
21461 is composite. Its prime factorisation is
- 3
The divisors add up to 23424; without 21461 itself that is 1963, so 21461 is deficient (1963 is less than 21461). Euler's totient φ(21461) = 19500 numbers up to 21461 share no factor with it.
- 4
The digits of 21461 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 74 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21461 = 11 \times 1951 \]
21461 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 23424 |
| Euler totient φ(n) | 19500 |
| Square | 460574521 |
| Cube | 9884389795181 |
| Square root | 146.495734 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 74 |
| Scientific notation | 2.1461 × |
21461 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand four hundred and sixty-one |
| Binary (base 2) | 101001111010101 |
| Octal (base 8) | 51725 |
| Hexadecimal (base 16) | 53D5 |
| Base 3 | 1002102212 |
| As time | 21461 seconds = 5 h 57 min 41 s |
Is 21461 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 2) | 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 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 5) | 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 | Yes (21461 ÷ 11 = 1951) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21461 a prime number?
No. 21461 = 11 × 1951, so it is divisible by 11.
What are the factors of 21461?
1, 11, 1951, 21461.
What is 21461 in binary?
101001111010101 (hexadecimal 53D5, octal 51725).
What is the square root of 21461?
About 146.4957.
Is 21461 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 21461?
21461 is a semiprime: 11 × 1951, the product of two primes.