Решето Эратосфена

def get_all_prime(n):
    a = [i for i in range(n+1)]
    a[1] = 0
    for i in range(2,n+1):
        if a[i] != 0:
            for j in range(2*i,n+1,i):
                a[j] = 0
    a = set(a)
    a.remove(0)
    return a


prime = get_all_prime(20000000)
print(prime)