Prove that prime numbers are infinite

Prove that prime numbers are infinite

To the contrary:
Suppose that the prime number is finite, we can use P1, P2 , PN to represent these primes
Any other number is a compound number, and prime numbers P1, P2 At least one of PN can divide it
Construct a number a, let it compare P1, P2 Any one of them is big, so it is different from any one of them
Let a = p1p2 × ×pn+1
But a cannot be replaced by P1, P2 So a is a prime, which is the same as that the prime has only P1, P2 , PN contradiction
So prime numbers are infinite