Prime factorization is when you break down the factors of 73 to just the prime factors and expressing 73 as a product of those prime factors.
In this case, because 73 is a prime number, we can simply state the primary factorization as 73.
For most numbers, we would take the smallest prime factor that is larger than 1 to start to break down the focus number. In this case, the smallest prime factor larger than 1 is 73.
73 ÷ 73 = 1
If we divide 73 by 73, we simply get 1, which can’t be broken down any further.
So, the prime factorization of 73 is just 73.