The number 21553
21553 is a composite number with 4 divisors. Its prime factorisation is 7 × 3079. Divisors (4): 1, 7, 3079, 21553.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21553: a semiprime: 7 × 3079, the product of two primes.
- 2
21553 is composite. Its prime factorisation is
- 3
The divisors add up to 24640; without 21553 itself that is 3087, so 21553 is deficient (3087 is less than 21553). Euler's totient φ(21553) = 18468 numbers up to 21553 share no factor with it.
- 4
The digits of 21553 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21553 = 7 \times 3079 \]
21553 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 24640 |
| Euler totient φ(n) | 18468 |
| Square | 464531809 |
| Cube | 10012054079377 |
| Square root | 146.809400 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1553 × |
21553 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and fifty-three |
| Binary (base 2) | 101010000110001 |
| Octal (base 8) | 52061 |
| Hexadecimal (base 16) | 5431 |
| Base 3 | 1002120021 |
| As time | 21553 seconds = 5 h 59 min 13 s |
Is 21553 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 3) | 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 | Yes (21553 ÷ 7 = 3079) | 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 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 3) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | 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 21553 a prime number?
No. 21553 = 7 × 3079, so it is divisible by 7.
What are the factors of 21553?
1, 7, 3079, 21553.
What is 21553 in binary?
101010000110001 (hexadecimal 5431, octal 52061).
What is the square root of 21553?
About 146.8094.
Is 21553 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 21553?
21553 is a semiprime: 7 × 3079, the product of two primes.