The first two consecutive numbers to have two distinct prime factors are:

14 = 2 x 7
15 = 3 x 5

The first three consecutive numbers to have three distinct prime factors are:

644 = 2² x 7 x 23
645 = 3 x 5 x 43
646 = 2 x 17 x 19.

Find the first four consecutive integers to have four distinct primes factors. What is the first of these numbers?

即找出先出現的連續四個數且都由四個質數構成.