a formula that will reverse the order of the digits in a number?

Question

example:
12345=54321
38507=70583
43580=can be 8534

Answer 1

I think that you can make an equation to do this, but I think that it depends on the number of digits. The equation would have to be adjusted for longer or shorter numbers.

I will need to use the modulus operator, which is somewhat rare. Is yields the remainder of two numbers if divided 10 % 3 = 1, 8 % 5 = 3, etc.

I have no idea how to simplify these equations.

For 2 digit numbers
f(x) = (10)(x % 10) + (x - (x % 10)) / 10

For 3 digit numbers
f(x) = (100)(x % 10) + ((x - (x % 10)) % 100) + (x - (x % 100)) / 100

For 4 digit numbers
f(x) = (1000)(x % 10) + ((x - (x % 10)) % 100) * 10 + ((x - (x % 100)) % 1000) / 10 + (x - (x % 1000)) / 1000

For 5 digit numbers
f(x) = (10000)(x % 10) + ((x - (x % 10)) % 100) * 100 + ((x - (x % 100)) % 1000) + ((x - (x % 1000)) % 10000) / 100 + (x - (x % 10000)) / 10000

Answer 2

1

Answer 3

2

Answer 4

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You could probably set up a spreadsheet to generate the numbers from 1 to 9999. (10000 not being symmetrical) Then using a formula to take the number and reverse it and compare it to the original number. For a five digit number strip the first then second then third digits etc, into five separate columns. Then you concatenate the columns in reverse to produce a reversed version of the original number. Use MID to extract the numbers into their component parts. Then check it against the original text entry. If it reverses and is true, a 1 is placed in a check cell to confirm the match with nothing placed in the column ( "" ) if there is no match Then you simply sort by the columns of 1s (MK) in ascending order followed by the actual symmetrical numbers (NUM) in ascending order. I'm actually working on this now. You will need 5 sheets set up. The first deals with single digit numbers. The second, two digit numbers, the third, three digit, etc. Okay: done it. This is for a 3-digit number check. The '[ ]' symbols represent cells. [ NUM ][ DIGIT1 ][ DIGIT2 ][ DIGIT3 ][ RNUM ][ CHK ][ MARK ] [ 111 ][ 1 ][ 1 ][ 1 ][ 111 ][ TRUE ][ 1 ] [ 211 ][ 2 ][ 1 ][ 1 ][ 112 ][FALSE][ ] Formulas [ 111 ][=MID($A2,1,1)][=MID($A2,2,1)][=MID($A2... ][=EXACT(A2,E2)][ 1 ] [ 211 ][=MID($A2,1,1)][=MID($A2,2,1)][=MID($A2... ][=EXACT(A2,E2)][] This what you put in each column - the text above is being shortened.. [Square brackets] indicate the contents of the cell. (Parentheses) indicate the spreadsheet cell reference. Example: In Cell A1, type NUM In Cell A2, type 111 In Cell B1, type DIGIT1 In Cell B2, type =MID($A2,1,1) and so on [ NUM ](A1) = [ 111 ](A2) [ DIGIT1 ](B1) = [=MID($A2,1,1)](B2) [ DIGIT2 ](C1) = [=MID($A2,2,1)](C2) [ DIGIT3 ](D1) = [=MID($A2,3,1)](D2) [ RNUM ](E1) = [=CONCATENATE(D2,C2,B2)](E2) [ CHK ](F1) = [=EXACT(A2,E2)](F2) [ MARK ](G1) = [ 1 ](G2) Just done it... For 1-digit numbers (9): - 1, 2, 3, 4, 5, 6, 7, 8, 9 For 2-digit numbers (9): - 11, 22, 33, 44, 55, 66, 77, 88, 99 For 3-digit numbers between 100 and 999, here is the list of 90 numbers: - 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484, 494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595, 606, 616, 626, 636, 646, 656, 666, 676, 686, 696, 707, 717, 727, 737, 747, 757, 767, 777, 787, 797, 808, 818, 828, 838, 848, 858, 868, 878, 888, 898, 909, 919, 929, 939, 949, 959, 969, 979, 989, 999 For 4-digit numbers (90): - 1001, 1111, 1221, 1331, 1441, 1551, 1661, 1771, 1881, 1991, 2002, 2112, 2222, 2332, 2442, 2552, 2662, 2772, 2882, 2992, 3003, 3113, 3223, 3333, 3443, 3553, 3663, 3773, 3883, 3993, 4004, 4114, 4224, 4334, 4444, 4554, 4664, 4774, 4884, 4994, 5005, 5115, 5225, 5335, 5445, 5555, 5665, 5775, 5885, 5995, 6006, 6116, 6226, 6336, 6446, 6556, 6666, 6776, 6886, 6996, 7007, 7117, 7227, 7337, 7447, 7557, 7667, 7777, 7887, 7997, 8008, 8118, 8228, 8338, 8448, 8558, 8668, 8778, 8888, 8998, 9009, 9119, 9229, 9339, 9449, 9559, 9669, 9779, 9889, 9999 Total 198 It's easy to adapt for 1, 2, 4, 5 or more digit numbers.

Answer 5

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Answer 6

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RE:
a formula that will reverse the order of the digits in a number?
example:
12345=54321
38507=70583
43580=can be 8534

Answer 7

I'm pretty sure there isn't a single formula that can do that (99.991618% sure...), unless it has many many many conditions, and the conditions might even have to be infinite in number so you would need a pattern for conditions, which is completely possible of coarse. Look at what Wiles did with his proof, had to prove an infinite number of sets, as well as an infinite number of sets within each of those infinite sets ^_^

Well, something like that at least, but I'm pretty sure that that's right.

Answer 8

You have to write a little computer program to do it with a small rutine that divides the number by 10*(the number of digits-1) then picks the number without decimals and so on untill the last digit..

Answer 9

3

Answer 10

Using a computer program:

Convert it to text.
Determine the length
. Grab the last character and append it to a string
. Repeat until done
Convert back to a number