There is only one prime factorization string for each number, so there is not a "longest" one. Since 239 is a prime number, its prime factorization is 239.
The prime factorization.
What is the longest prime factorization of 50?
The prime factorization
The longest factor string of any composite number is its prime factorization.
The prime factorization of 99999 is 3 x 3 x 41 x 271
99,999=3x3x41x271
The prime factorization.
16
The largest 5-digit whole number is 99,999. Its prime factorization is: 3 x 3 x 41 x 271
For composite numbers, only one string of factors is the longest; the prime factorization.
The prime factorization is the longest factor sting.