# Prime factors of number

Python, Math, Algorithm · May 24, 2023

Finds and returns the list of prime factors of a number.

- Use a
`while`

loop to iterate over all possible prime factors, starting with`2`

. - If the current
`factor`

exactly divides`num`

, add`factor`

to the`factors`

list and divide`num`

by`factor`

. Otherwise, increment`factor`

by one.

```
def prime_factors(num):
factors = []
factor = 2
while (num >= 2):
if (num % factor == 0):
factors.append(factor)
num = num / factor
else:
factor += 1
return factors
```

```
prime_factors(12) # [2,2,3]
prime_factors(42) # [2,3,7]
```