The number 15551
15551 is a palindromic prime: it reads the same backwards and is prime, the 1814th prime number and a palindrome: it reads 15551 backwards too. Its only divisors are 1 and 15551.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 15551: a palindromic prime: it reads the same backwards and is prime; the 1814th prime number; a palindrome: it reads 15551 backwards too.
- 2
15551 is prime, so its only factors are 1 and 15551. It is the 1814th prime; the next prime is 15559 and the one before is 15541.
- 3
The divisors add up to 15552; without 15551 itself that is 1, so 15551 is deficient (1 is less than 15551). Euler's totient φ(15551) = 15550 numbers up to 15551 share no factor with it.
- 4
The digits of 15551 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 146 steps to reach 1.
15551 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 15552 |
| Euler totient φ(n) | 15550 |
| Square | 241833601 |
| Cube | 3760754329151 |
| Square root | 124.703649 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 146 |
| Scientific notation | 1.5551 × |
15551 in other forms
| Form | Value |
|---|---|
| In words | fifteen thousand five hundred and fifty-one |
| Binary (base 2) | 11110010111111 |
| Octal (base 8) | 36277 |
| Hexadecimal (base 16) | 3CBF |
| Base 3 | 210022222 |
| As time | 15551 seconds = 4 h 19 min 11 s |
Is 15551 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 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 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | 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 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 15551 a prime number?
Yes. 15551 is divisible only by 1 and itself.
What are the factors of 15551?
1, 15551.
What is 15551 in binary?
11110010111111 (hexadecimal 3CBF, octal 36277).
What is the square root of 15551?
About 124.7036.
Is 15551 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 15551?
15551 is a palindromic prime: it reads the same backwards and is prime; the 1814th prime number; a palindrome: it reads 15551 backwards too.