The number 145
145 is a composite number with 4 divisors. Its prime factorisation is 5 × 29. Divisors (4): 1, 5, 29, 145.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 145: a semiprime: 5 × 29, the product of two primes.
- 2
145 is composite. Its prime factorisation is
- 3
The divisors add up to 180; without 145 itself that is 35, so 145 is deficient (35 is less than 145). Euler's totient φ(145) = 112 numbers up to 145 share no factor with it.
- 4
The digits of 145 add up to 10, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 116 steps to reach 1.
LaTeX source of the formulas on this page
\[ 145 = 5 \times 29 \]
145 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 180 |
| Euler totient φ(n) | 112 |
| Square | 21025 |
| Cube | 3048625 |
| Square root | 12.041595 |
| Digit sum / digital root | 10 / 1 |
| Collatz steps to 1 | 116 |
| Scientific notation | 1.45 × |
145 in other forms
| Form | Value |
|---|---|
| In words | one hundred and forty-five |
| Roman numerals | CXLV |
| Binary (base 2) | 10010001 |
| Octal (base 8) | 221 |
| Hexadecimal (base 16) | 91 |
| Base 3 | 12101 |
| As time | 145 seconds = 2 min 25 s |
Is 145 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 | Yes (145 ÷ 5 = 29) | 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 5) | 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 1) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | 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 145 a prime number?
No. 145 = 5 × 29, so it is divisible by 5.
What are the factors of 145?
1, 5, 29, 145.
What is 145 in binary?
10010001 (hexadecimal 91, octal 221).
What is the square root of 145?
About 12.0416.
What is 145 in Roman numerals?
CXLV.
Is 145 divisible by 3?
No. Its digits add up to 10, which is not a multiple of 3.
What is special about the number 145?
145 is a semiprime: 5 × 29, the product of two primes.