$3 、$ Prime numbers or primes are natural numbers greater than 1 that can only be divided by 1 and themselves, like $2 、 3 、 5 、 7$. Every natural number can be expressed as a product of several primes (which may be the same), for example: $4=2 \times 2,6=2 \times 3,8=2 \times 2 \times 2$, $9=3 \times 3,10=2 \times 5$, etc. Therefore, $2 \times 3 \times 5 \times 7-1$ written in this form is $\qquad$
【Analysis】 $2 \times 3 \times 5 \times 7-1=209=11 \times 19$