[QUOTE=Uncwilly]Yeah, 386 + 15 = 401 (and since the start of each number is low, 1 and 2, you will lose one digit, like I showed above).[/QUOTE]

Not sure I totally understand... but correct me if I am wrong. The 386 number from above is How many digits total. But Below, I am seeing e+385, is that because to make 386 I would add the 1. to the 385 to = 386?
In turn if the number was 2.some long number e+385 would be 387 digits.


[QUOTE]The e+385 part of the number above is the same as writing 'x 10[sup]385[/sup]'. [/QUOTE]

Thanks so much for taking the time out to help me understand.

When you see a letter and parenth like: R( )
It means that there is a 'function' called 'R'. Which is way of taking a starting number and converting it into another. A function is a series of math operations, plain and simple. It can be as simple as adding 1 to a number or so complex that you can hardly follow it.

If you had a function Kg that converted pounds to kilograms it would look like this.
Kg(x) = x / 2.2
Which means that you take a number (represented by 'x') and divide it by 2.2

In this forum when we use the M function, we are refering to the Mersenne function.
M(x)=2[sup]x[/sup]-1

C refers to a Cunningham number, if i recall correctly. Which is just a group of numbers that have some property that a fellow named Cunningham was interested in. Imagine if you take a number and run it through the M function then take the result and run [B]that[/B] through the M function. That is what it is. There are a bunch of folks trying to figure if this continues to generate numbers that are prime.

[quote]If 2^127 = 170141183460469231731687303715884105727 then why when calculated on my computer it comes up as
17014118346046923173168730371588e+38[/quote]Simple, your calculator can't handle a number that big without using the shorthand, my old TI-35 calculator would have shown it as [FONT=Impact]1.701411834 [sup]38[/sup][/FONT]

You are starting to hop right into some challenging areas of math. Don't worry too much if you don't understand everything right away. Math uses Greek letters for things, like you may know that 'pi' is 3.1415926.....
Sometimes the same Greek letter is used to mean different things in different contexts.

If you take a number like: 9.87654 x 10^5
just work the math in the correct order.
9.87654 x 10^5 = 9.87654 x 100000
9.87654 x 100000 = 987654

It is a way of writing the number. Often people may use 10^6, 10^9, 10^12 to put things in millions, billions, and trillions.
So you may see 123.23 x 10^12 it is the same as 1.2323 x 10[sup]14[/sup].
It is often useful to keep numbers in a single size, even if it is 10's or 100's of millions, but not trillions.

Just like in the meteric system a letter is used.
1000 grams is 1 kilogram (1Kg)
1000 Kg is 1 Megagram (1Mg)
1/1000 of a gram is 1 milligram (1mg)


BTW, I am not nearly as math smart as some of the brains here. Fractions got me too when I first started studying them.

[QUOTE=Unregistered]Not sure I totally understand... but correct me if I am wrong. The 386 number from above is How many digits total. But Below, I am seeing e+385, is that because to make 386 I would add the 1. to the 385 to = 386?
In turn if the number was 2.some long number e+385 would be 387 digits.
QUOTE]

The actual digit at the beginning does not change the number of digits in the whole thing.

"2^1279-1 = 1.0407932094664399081925240327364e+385"

In this number, the e+385 means that there are 385 digits after the decimal point. In this form, called "scientific notation," there is alwas just one digit to the left of the decimal point. So regardless of what that digit is, the e+385 means that there are a total of 386 digits in the figure.

[QUOTE=Unregistered]In turn if the number was 2.some long number e+385 would be 387 digits?[/QUOTE]

I am sorry that in my haste to post I failed to notice this part of the question.

No matter how many digits are on the left of the decimal (usually 1, but at times 2,3, or even 4) simpley count them (don't worry about their value) and add that to the e+385, or what ever it may be.

Examples:
2.345e+3 = 2345 (4 digits long)
1.234e+3 = 1234 (4 digits long)

16.5 million = 16,500,000 (8 digits)
16.5 x 10[sup]6[/sup] = 16,500,000 (8 digits)
16.5e+6 = 16,500,000 (8 digits)
1.65e+7 = 16,500,000 (8 digits)
1.65 x 10^7 = 16,500,000 (8 digits)
7.89 x 10^7 = 78,900,000 (8 digits)
7.89e+7 = 78,900,000 (8 digits)

:smile: