<?

$n=100;

$i=$n-1;

for($i;$i>=1;--$i){

    echo $n." X ".$i."<br>";

    $n = ($n*$i);

    

}

echo "____________ ="."<br>";

echo $n;

?>

100 X 99

9900 X 98

970200 X 97

94109400 X 96

9034502400 X 95

858277728000 X 94

80678106432000 X 93

7503063898176000 X 92

690281878632192000 X 91

6.2815650955529E+19 X 90

5.6534085859977E+21 X 89

5.0315336415379E+23 X 88

4.4277496045534E+25 X 87

3.8521421559614E+27 X 86

3.3128422541268E+29 X 85

2.8159159160078E+31 X 84

2.3653693694466E+33 X 83

1.9632565766406E+35 X 82

1.6098703928453E+37 X 81

1.3039950182047E+39 X 80

1.0431960145638E+41 X 79

8.2412485150538E+42 X 78

6.428173841742E+44 X 77

4.9496938581413E+46 X 76

3.7617673321874E+48 X 75

2.8213254991405E+50 X 74

2.087780869364E+52 X 73

1.5240800346357E+54 X 72

1.0973376249377E+56 X 71

7.7910971370578E+57 X 70

5.4537679959405E+59 X 69

3.7630999171989E+61 X 68

2.5589079436953E+63 X 67

1.7144683222758E+65 X 66

1.131549092702E+67 X 65

7.3550691025633E+68 X 64

4.7072442256405E+70 X 63

2.9655638621535E+72 X 62

1.8386495945352E+74 X 61

1.1215762526665E+76 X 60

6.7294575159988E+77 X 59

3.9703799344393E+79 X 58

2.3028203619748E+81 X 57

1.3126076063256E+83 X 56

7.3506025954235E+84 X 55

4.0428314274829E+86 X 54

2.1831289708408E+88 X 53

1.1570583545456E+90 X 52

6.0167034436372E+91 X 51

3.068518756255E+93 X 50

1.5342593781275E+95 X 49

7.5178709528247E+96 X 48

3.6085780573558E+98 X 47

1.6960316869572E+100 X 46

7.8017457600033E+101 X 45

3.5107855920015E+103 X 44

1.5447456604807E+105 X 43

6.6424063400668E+106 X 42

2.7898106628281E+108 X 41

1.1438223717595E+110 X 40

4.575289487038E+111 X 39

1.7843628999448E+113 X 38

6.7805790197904E+114 X 37

2.5088142373224E+116 X 36

9.0317312543608E+117 X 35

3.1611059390263E+119 X 34

1.0747760192689E+121 X 33

3.5467608635875E+122 X 32

1.134963476348E+124 X 31

3.5183867766788E+125 X 30

1.0555160330036E+127 X 29

3.0609964957105E+128 X 28

8.5707901879895E+129 X 27

2.3141133507572E+131 X 26

6.0166947119686E+132 X 25

1.5041736779922E+134 X 24

3.6100168271812E+135 X 23

8.3030387025167E+136 X 22

1.8266685145537E+138 X 21

3.8360038805627E+139 X 20

7.6720077611254E+140 X 19

1.4576814746138E+142 X 18

2.6238266543049E+143 X 17

4.4605053123183E+144 X 16

7.1368084997093E+145 X 15

1.0705212749564E+147 X 14

1.498729784939E+148 X 13

1.9483487204206E+149 X 12

2.3380184645048E+150 X 11

2.5718203109553E+151 X 10

2.5718203109553E+152 X 9

2.3146382798597E+153 X 8

1.8517106238878E+154 X 7

1.2961974367214E+155 X 6

7.7771846203287E+155 X 5

3.8885923101643E+156 X 4

1.5554369240657E+157 X 3

4.6663107721972E+157 X 2

9.3326215443944E+157 X 1

____________ =

9.3326215443944E+157

//Funzione

function trovaZeri($n){

    $d=5;

    $zeri=0;

    $r=$n;

    $i=1;

    

    while($r>=1){

    $r=($n/pow($d,$i));

    $zeri+=intval($r);

    $i++;

    }

    echo "Numero analizzato: ".$n."! <br>";

    echo "Zeri finali: ".$zeri;

}



//Fa partire la funzione. Per analizzare altri numeri basta cambiare il numero tra parentesi.

trovaZeri(100);

Numero analizzato: 100!

Zeri finali: 24