输出结果无法达到预期，好像是返还值的问题？

问题：设计一个函数集合器(设计一个菜单),包含以下各功能模块:

1. 水数仙花
2. 完数
3. 素数
4. 公约数与公倍数
5. 哥德巴赫猜想
6. 猴子吃桃

#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
int prime(int) { return 1; }
int Prime(int) { return 1; }
int hanshu1()
{ int a,b,c,number;
  for (number=100;number<1000;number++)
  {
      a = number / 100;
      b = number / 10 % 10;
      c = number % 10;
      if (a * a * a + b * b * b + c * c * c == number) cout << number << endl;
  }
    return 0;
}
int hanshu2()
{
    int sum = 0;
    int n; cout << "判断输入是否是完数" << endl;
    cin >> n;
    for (int i = 1;i < n;i++) 
    { if (n % i == 0) { sum += i; }
    if (sum == n)
    {
        cout << "是完数" << endl;
    }
    else cout << "不是完数" << endl;
    }
    return 0;
}
int hanshu3()
{
    int m, k, i, n = 0;
    bool prime;
    for(m=101;m<=200;m+=2)
    {
        prime = true;k = int(sqrt(m));
        for(i=2;i<=k;i++)
            if(m%i==0)
            {
                prime = false;break;
            }
        if (prime) {
            cout << setw(5) << m;
            n += 1;
        }
        if (n % 10 == 0)cout << endl;
    }
    return 0;
}
int hanshu4()
{
    int m, n, r;
    cout << "输入俩个数";
    cin >> m >> n;
    int s = m * n;
    r = m % n;
    while(r!=0)
    {
        m = n;
        n = r;
        r = m % n;
    }
    cout << "最大公倍数" << n << endl;
    cout << "最小公倍数" << s/n << endl;
    return 0;
}
int hanshu5()
{
    long i, j, k, flag1, flag2, n = 0;
    int a, b;
    int Prime(int);
    cout << "请输入要验证的偶数范围，即输入两个正偶数:";
    cin >> a >> b;
    int min = a <= b ? a : b;
    int max = a >= b ? a : b;
    for(i=min;i<=max;i+=2)
    {
        for (i = min;i<=max;i+=2)
        {
            for (k = 2;k<=i/2;k++)
            {
                j = i - k;flag1 = Prime(k);
                if(flag1)
                {
                    flag2 = Prime(j);
                    if(flag2)
                    {
                        cout << i << "=" << j << "+" << k << " ";
                        n++;
                        if (n % 5 == 0)cout << endl;break;
                    }
                }
            }
        }
    }
    cout << "哥德巴赫猜想正确！"<<endl;
    return 0;
}
int hanshu6()
{
    int a, b = 1;
    for(int i=1;i<10;i++)
    {
        a = (b + 1) * 2;
        b = a;
    }
    cout << "第一天摘的桃子有" << a << "个" << endl;
    system("pause");
    return 0;
}
int main()
{
    int a;
    cout << "1)    水数仙花" << endl;
    cout << "2)    完数" << endl;
    cout << "3)    素数" << endl;
    cout << "4)    公约数与公倍数" << endl;
    cout << "5)    哥德巴赫猜想" << endl;
    cout << "6)    猴子吃桃" << endl;
        cout << "请选择";
    cin >> a;
    switch(a)
    {
    case 1:hanshu1;break;
    case 2:hanshu2;break;
    case 3:hanshu3;break;
    case 4:hanshu4;break;
    case 5:hanshu5;break;
    case 6:hanshu6;break;
    default:cout << "错误！" << endl;
    }
    return 0;
}

将主函数改为

int main()
{
  cout << "请选择";
 cin >> a;
 switch(a)
 {
 case 1:hanshu1();break;
 case 2:hanshu2();break;
 case 3:hanshu3();break;
 case 4:hanshu4();break;
 case 5:hanshu5();break;
 case 6:hanshu6();break;
 default:cout << "错误！" << endl;
 }
 return 0;
}

主要是函数调用时的子函数括号没有加上。