1. k=0;
2. n==1まで以下を繰り返す
3. for(m=2;n%m;m++);
4. n/=m;
5. k+=m

#include <stdio.h>

int main(void)
{
    unsigned n=2004,m;
    while(n>1) {
        for(m=2;n%m;m++);
        n/=m;
        printf("%d\n",m);
    }
    return 0;
}

• 二つのunsigned型の変数nとmを宣言かつ定義しています。
• 変数nを2004に初期化しています。

#include <stdio.h>

int main(void)
{
    int n, i, s;

    while (scanf("%d", &n) == 1 && n > 0) {
        printf(" 1"), s = 1;
        for (i = 2; i <= n; i++)
            if (n % i == 0) printf(" + %d", i), s += i;
        printf(" = %d\n", s);
    }
    return 0;
}

#include <stdio.h>
#include <stdlib.h>

typedef struct List{
    unsigned no,count;
    struct List *next;
} List;

List *mkList(unsigned data)
{
    static List end = {0,0,NULL};
    List *retptr = &end;
    unsigned no = 2;
    for (;no*no <= data;no++) {
        
        if (retptr->count != 0) {
            List *last = malloc (sizeof (List));
            last->count = 0;
            last->next = retptr;
            retptr = last;
        }
        retptr->no = no;
        while (data%no == 0) {
            retptr->count++;
            data/=no;
            printf(" %u ",no);
        }
    }
    if (data != 1) {
        List *last = malloc (sizeof (List));
        last->count = 1;
        last->no = data;
        last->next = retptr;
        retptr = last;
        printf("%u",data);
    }
    return retptr;
}
void printList(List *list)
{
    printf("\n");
    while (list) {
        printf("%u * %u\n",list->no,list->count);
        list = list->next;
    }
}
unsigned answer(List *list,unsigned no)
{
    unsigned ret = 0;
    unsigned count;
    for (count = 0;count<=list->count;no *= list->no,++count) {
        if (list->next)
            ret += answer(list->next,no);
        else
            ret += no;
    }
    return ret; 
}
int main()
{
    unsigned indata;
    List *start;
    printf("Input Data:");
    scanf("%u",&indata);
    printf("%u の分解は、\n",indata);
    start = mkList(indata);
    printList(start);
    printf("答えは:%u\n",answer(start,1));
    return 0;
}

List *ListAlloc(List *next)
{
    List *retptr = malloc(sizeof (List));
    if (!retptr) {
        fprintf(stderr,"malloc error!!\n");
        exit(1);
    }
    retptr->no = retptr->count = 0;
    retptr->next = next;
    return retptr;
}
List *mkList(unsigned data)
{
    unsigned no = 2;
    List *retptr = ListAlloc(NULL);
    retptr->no = no;
    while (data % no == 0) {
        retptr->count++;
        data/=no;
    }
    for (no++;no*no <= data;no+=2) {
        if (retptr->count)
            retptr = ListAlloc(retptr);
        retptr->no = no;
        while (data % no == 0) {
            retptr->count++;
            data /= no;
        }
    }
    if (data != 1) {
        if (retptr->count)
            retptr = ListAlloc(retptr);
        retptr->no = data;
        retptr->count = 1;
    }
    return retptr;
}

#include <iostream>
#include <map>

using namespace std;

struct S { map<int, int> a; int sum; };

void  func2(S &s, map<int, int>::iterator p, int d)
{
    if (p == s.a.end()) {
        s.sum += d;
        cout << (d==1 ? " " : " + ") << d;
    }
    else {
        int n = p->second, v = p->first, k = 1, i = 0;
        for (++p; i <= n; i++, k *= v)
            func2(s, p, d * k);
    }
}

void func(int n)
{
    S s;  int i = 2;
    while (i <= n)
        if (n % i) i++;  else n /= i, s.a[i]++;
    map<int, int>::iterator p = s.a.begin();
    cout << "  = " << p->first << "^" << p->second;
    if (p != s.a.end())
        while (++p != s.a.end())
            cout << " * " << p->first << "^" << p->second;
    cout << endl;
    s.sum = 0;
    func2(s, s.a.begin(), 1);
    cout << " = " << s.sum << endl;
}

int main()
{
    int n;
    while (cin >> n) func(n);
}

#include <stdio.h>

unsigned pw(unsigned x,unsigned y)
{
    unsigned i,r;
    for(i=0,r=1;i<y;i++) r*=x;
    return r;
}

int main(void)
{
    unsigned n,m=0,k=1,r,l,pm=3;
    printf("n=");
    scanf("%d",&n);
    for(r=1;n>1&&n%2==0;r++) n/=2;
    l=1;
    while(--r) l+=pw(2,r);
    k*=l;
    for(r=1;n>1;) {
        for(m=pm;n%m;m+=2);
        if(m==pm) r++;
        else {
            l=1;
            while(--r) l+=pw(pm,r);
            k*=l;
            pm=m;
            r=2;
        }
        n/=m;
    }
    l=1;
    while(--r) l+=pw(m,r);
    k*=l;
    printf("k=%d\n",k);
    return 0;
}

#include <stdio.h>

int main(void)
{
    int n;
    while (scanf("%d", &n) == 1) {
        int i = 2, c = 0, s = 1, k = 1, p = 1;
        while (i <= n)
            if (n % i) {
                if (c) p *= s;
                i++, c = 0, s = k = 1;
            }
            else
                c++, k *= i, s += k, n /= i;
        if (c) p *= s;
        printf("  %d\n", p);
    }
    return 0;
}

>               if (c) p *= s;
>               i++, c = 0, s = k = 1;
を
                if (c) p *= s, c = 0, s = k = 1;
                i++;
に訂正します。