Please tell me what is 15 factorial?

Question

When I try to find factorial of large numbers I get a really weird answer and I have no way to interpret it. For example plugged in 15! in my calculator and answer 1.3076744e + 12. What on earth is that?

Answer 1

15 factorial is ...



15! = 1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 * 9 * 10 * 11 * 12 * 13 * 14 * 15



So let me just ask R:



> factorial(15)

[1] 1.307674e+12



> prod(1:15)

[1] 1.307674e+12



Huh, it seems like R might round this a bit.

Maybe I should ask Perl.

----------------------

Alright Perl gave me an answer:

Alright, I figured out that if I include the bignum library then perl can give me the exact value of very large factorials.



#!/usr/bin/env perl

# This badass perl calculator will calculate the value of n!

# especially when the input is 15! it won't approximate!

use warnings;

use bignum;



print "Please Enter a number to calculate the factorial of:\n";

chomp(my $number = );



my $i = 1; # start counter at 1.

my $factorial = 1;

while($i < $number)

{

$i = $i + 1;

$factorial = $factorial * $i;

}

print "The value of $number! is $factorial\n";

##########################################

######## END OF PERL CODE BLOCK ########





When the standard input is 15 this is what I get.



Please Enter a number to calculate the factorial of:

15

The value of 15! is 1307674368000



There is your answer.



15! = 1307674368000



# The example perl scripts included for-loops, so I wrote a program to give the while loop some love!!!

Answer 2

15 ! = 15 * 14 * 13 .......... * 3 * 2 * 1 = 1307674368000 answer//

Answer 3

15!

= 1307674368000

= 1.307674368 × 10^12

Answer 4

15! is actually the multiplication of all its preceeding terms with one another.

i.e. 15 x 14 x 13 x 12 x.........x 1

Your answer will be 1.307 x 10 ¹²

Answer 5

The full answer is 1,307,674,368,000 which is 1 trillion 307 billion 674 million 368 thousand.



But your calculator can't handle a number that large, at least not with complete precision out to 13 digits. So it gives you an approximate answer of 1.3076744E12



You can think of the number after E as the number of places you'd have to move the decimal point to get close to the actual answer. In your case, it is saying 12 places which would give an approximate answer of 1,307,674,400,000.



That's close but not the exact answer. So don't rely on your calculator for really​ big (or really small) numbers.

Answer 6

It's about 1.31 trillion in the American way of speaking.

Answer 7

factorial 3 = 1*2*3

factorial 4 = 1*2*3*4

factorial 5 = 1*2*3*4*5

Answer 8

That is Scientific Notation (US) or Standard Form elsewhere.



n.nnnnnnn x 10^n is the general format.



Some calculators, and web sites, use the 'E' notation.



1.3076744e + 12

= 1307674400000



It simply means to move the decimal over that much.

Answer 9

　

1.3076744e+12 means 1.3076744 × 10^12

It's the way calculators use to display numbers that are otherwise too large to display.



Your calculator seems to only display 8 significant digits



I used my computer's calculator, which displays more digits, and got:

15! = 1,307,674,368,000 = 1.307674368 × 10^12 ≈ 1.3076744 × 10^12

Answer 10

That's about 1.3 * 10^12



Whenever you get e+12, that's your calculator's way of saying, "I can't display this many digits." At that point, it's taken to using a form of scientific notation



15! =>

15 * 14 * 13 * 12 * 11 * 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1 =>

3 * 14 * 13 * 12 * 11 * 10 * 5 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 =>

14 * 13 * 12 * 11 * 9 * 8 * 7 * 6 * 4 * 3 * 3 * 10 * 5 * 5 * 2 =>

13 * 12 * 11 * 9 * 8 * 7 * 7 * 6 * 4 * 3 * 3 * 10 * 5 * 2 * 5 * 2 =>

156 * 99 * 8 * 49 * 24 * 9 * 1000 =>

156 * 8 * 49 * 24 * 99 * 9 * 1000 =>

1248 * 24 * 49 * 99 * 9 * 1000 =>

1248 * (25 - 1) * 49 * 99 * 9 * 1000 =>

(1248 * 100/4 - 1248) * 49 * 99 * 9 * 1000 =>

(312 * 100 - 1248) * 49 * 99 * 9 * 1000 =>

(31200 - 1248) * 49 * 99 * 9 * 1000 =>

(30000 - 48) * 49 * 99 * 9 * 1000 =>

29952 * 49 * 99 * 9 * 1000 =>

29952 * (50 - 1) * 99 * 9 * 1000 =>

(29952 * 50 - 29952 * 1) * 99 * 9 * 1000 =>

(14976 * 100 - 29952) * 99 * 9 * 1000 =>

(1497600 - 29952) * 99 * 9 * 1000 =>

(1497600 - 30000 + 48) * 99 * 9 * 1000 =>

(1497648 - 30000) * 99 * 9 * 1000 =>

1467648 * 99 * 9 * 1000 =>

1467648 * (100 - 1) * 9 * 1000 =>

(146764800 - 1467648) * (10 - 1) * 1000 =>

(140000000 + 6000000 - 1000000 + 760000 - 460000 + 4800 - 7648) * (10 - 1) * 1000 =>

(140000000 + 5000000 + 300000 + 4800 - 7600 - 48) * (10 - 1) * 1000 =>

(145300000 - 2848) * (10 - 1) * 1000 =>

(145297152) * (10 - 1) * 1000 =>

(1 452 971 520 - 145 297 152) * 1000 =>

(1 000 000 000 + 452 000 000 - 145 000 000 + 971 000 - 297 000 + 520 - 152) * 1000 =>

(1 000 000 000 + 307 000 000 + 674 000 + 368) * 1000 =>

(1 307 674 368) * 1000 =>

1 307 674 368 000

Answer 11

Fifteen factorial is represented by: 15!



15! = 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10

x 11 x 12 x 13 x 14 x 15



15! = 1,307,674,368,000

Answer 12

1.3076744e+12 means you should move the decimal point 12 places to the right.

Answer 13

15 factorial = 1.3076744e+12

Answer 14

Lol

Answer 15

It is really 1.31 trillion

Answer 16

1=5+6%9/23=-5

Answer 17

1=5+6%9/23=-5

Answer 18

1.3076744e+12 means you should move the decimal point 12 places to the right.

So it becomes 1,307,674,400,000. But your calculator's display doesn't have enough space to show all that.



The "e" means "exponent", as in 10^12.

Answer 19

15! has more digits than your calculator displays so it is presented as a floating point number.



1.3076744e + 12



e + 12 means × 10^(12)



1.3076744 × 10^(12)



15! = 1 307 674 368 000



Note that floating point values are often not exact so this is an approximation of the actual value.



Numbers that are too large or too small ore often displayed this way.

Answer 20

The answer is correct, if the number is too big/small and it can't be fully showed on calculator, it will be showed at this way.