The number 151
151 is a palindromic prime: it reads the same backwards and is prime, a twin prime (149 and 151 are both prime) and the 36th prime number. Its only divisors are 1 and 151.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 151: a palindromic prime: it reads the same backwards and is prime; a twin prime (149 and 151 are both prime); the 36th prime number; a palindrome: it reads 151 backwards too.
- 2
151 is prime, so its only factors are 1 and 151. It is the 36th prime; the next prime is 157 and the one before is 149.
- 3
The divisors add up to 152; without 151 itself that is 1, so 151 is deficient (1 is less than 151). Euler's totient φ(151) = 150 numbers up to 151 share no factor with it.
- 4
The digits of 151 add up to 7, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 15 steps to reach 1.
151 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 152 |
| Euler totient φ(n) | 150 |
| Square | 22801 |
| Cube | 3442951 |
| Square root | 12.288206 |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 15 |
| Scientific notation | 1.51 × |
151 in other forms
| Form | Value |
|---|---|
| In words | one hundred and fifty-one |
| Roman numerals | CLI |
| Binary (base 2) | 10010111 |
| Octal (base 8) | 227 |
| Hexadecimal (base 16) | 97 |
| Base 3 | 12121 |
| As time | 151 seconds = 2 min 31 s |
Is 151 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 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 1) | 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 7) | 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 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 151 a prime number?
Yes. 151 is divisible only by 1 and itself.
What are the factors of 151?
1, 151.
What is 151 in binary?
10010111 (hexadecimal 97, octal 227).
What is the square root of 151?
About 12.2882.
What is 151 in Roman numerals?
CLI.
Is 151 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 151?
151 is a palindromic prime: it reads the same backwards and is prime; a twin prime (149 and 151 are both prime); the 36th prime number; a palindrome: it reads 151 backwards too.