Multiply by the gables on Hawthorne's house.
Add the number that a stitch in time saves.
Add the number of blind mice.
Subtract the number of William Pene du Bois' balloons.
Add the number of wonders of the world.
Subtract the number of miles in Camptown's racetrack.
Subtract the number of strings on a violin.

Divide by the number of vertices on a regular hexahedron.
Add the number of the engine that ran on Chicago line.
Multiply by the number of gentlemen of Verona.
Add the atomic number of the element whose symbol is the 25th letter of the alphabet.
Divide by the number of hills of Rome.
Multiply by the number of railroads on a Monopoly board.
Add the number of easy pieces.
Add the number of chromosomes in a normal human muscle cell.

Multiply by the number of kittens that lost their mittens.
Add the number of acres in A.A.Milne's woods.
Multiply by the number of cities in Dickens' tale.
Subtract the number of degrees Fahrenheit at which Bradbury's books burn.
Add the number of Great Lakes.
Divide by the number of days of the condor in the title of Grady's book.
Subtract the number of blackbirds baked in a pie.
Multiply by the number of horsemen of the Apocalypse.

Divide by the number of men on a dead man's chest.
Add the number of a neutral PH.
Subtract the number of carbon atoms in a molecule of ethane.
Multiply by the number of heads on Lofting's Push-me-Pull-you.
Add the number of miles on the road sign to Juster's Digitopolis.
Subtract the number of dried orange pips in a Sherlock Holmes case.
Multiply by the number of the square at which Alice met Humpty Dumpty.
Divide by the number of witches in Macbeth.
Divide by the number of suits in a standard deck of cards.

What am I?

• I really like this puzzle, but I fear a lot of people won't since all it needs is basic arithmetic and some Googling - not enough of a challenge for them! Mar 3, 2015 at 12:06
• It also looks getting any answer wrong will totally mess up the solver, though the divisions are a bit of a check, assuming they give whole numbers.
– xnor
Mar 4, 2015 at 1:39

The answer is: You are Thirteen (13).

This community wiki provides a step-by-step solution for the 32 numbers:

• Start with an unlucky Friday number --> Friday 13th --> 13
• Multiply by the gables on Hawthorne's house --> The House of the Seven Gables --> 13*7=91
• Add the number that a stitch in time saves --> A stitch in time saves nine --> 91+9=100
• Add the number of blind mice. - Three blind mice --> 100+3=103
• Subtract the number of William Pene du Bois' balloons. ->- The Twenty-One Balloons --> 103-21=82
• Add the number of wonders of the world. --> Seven wonders of the world --> 82+7=89
• Subtract the number of miles in Camptown's racetrack. --> De Camptown race-track five miles long -- Oh! Doo-dah day! --> 89-5=84
• Subtract the number of strings on a violin. --> four strings on a violin --> 84-4=80

• Divide by the number of vertices on a regular hexahedron. --> a cube has 8 vertices --> 80/8=10
• Add the number of the engine that ran on Chicago line. --> Engine Engine Number Nine, going down Chicago line --> 10+9=19
• Multiply by the number of gentlemen of Verona. --> The Two Gentlemen of Verona by Shakespeare --> 19*2=38
• Add the atomic number of the element whose symbol is the 25th letter of the alphabet. --> atomic number of Y=Yttrium is 39 --> 38+39=77
• Divide by the number of hills of Rome. --> Rome was built on seven hills --> 77/7=11
• Multiply by the number of railroads on a Monopoly board. --> four railway stations on a Monopoly board --> 11*4=44
• Add the number of easy pieces. --> Five Easy Pieces --> 44+5=49
• Add the number of chromosomes in a normal human muscle cell. --> 46 chromosomes per cell --> 49+46=95

• Multiply by the number of kittens that lost their mittens. --> The three little kittens, they lost their mittens --> 95*3= 285;
• Add the number of acres in A.A.Milne's woods. --> Hundred Acre Wood --> 285+100=385
• Multiply by the number of cities in Dickens' tale. --> A Tale of Two Cities --> 385*2=770
• Subtract the number of degrees Fahrenheit at which Bradbury's books burn. --> Fahrenheit 451 --> 770-451=319
• Add the number of Great Lakes. --> The Five Great Lakes --> 319+5=324
• Divide by the number of days of the condor in the title of Grady's book. --> Six Days of the Condor --> 324/6=54
• Subtract the number of blackbirds baked in a pie. --> Four and twenty blackbirds baked in a pie --> 54-24=30
• Multiply by the number of horsemen of the Apocalypse. --> The Four Horsemen of the Apocalypse --> 30*4=120

• Divide by the number of men on a dead man's chest. --> Fifteen Men On The Dead Man's Chest --> 120/15=8
• Add the number of a neutral PH. --> A pH of 7 is neutral --> 8+7=15
• Subtract the number of carbon atoms in a molecule of ethane. --> Ethane is C2H6 --> 15-2=13
• Multiply by the number of heads on Lofting's Push-me-Pull-you. --> gazelle-unicorn cross which has two heads --> 13*2=26
• Add the number of miles on the road sign to Juster's Digitopolis. --> an enormous road sign, pointing in all three directions, stated clearly: DIGITOPOLIS 5 Miles --> 26+5=31
• Subtract the number of dried orange pips in a Sherlock Holmes case. --> The Five Orange Pips --> 31-5=26
• Multiply by the number of the square at which Alice met Humpty Dumpty. --> the Sixth square belongs to Humpty Dumpty --> 26*6=156
• Divide by the number of witches in Macbeth. --> The three weyward Sisters, hand in hand --> 156/3=52
• Divide by the number of suits in a standard deck of cards. --> spades, hearts, clubs, diamonds --> 52/4=13

details below...

The numbers are, in order:

13, 7, 9, 3, 21, 7, 5?, 4, 8, 9, 2, 39, 7, 4, 5?, 46, 3, 100, 2, 451, 5, 6, 24, 4, 15, 7, 2, 2, 5?, 5, 6, 3, 4.

58.6 (edit: 13).

I'm short on time now, but I'll edit this answer into a (much) nicer format later! Edit: user9914 and the omnipresent Gamow have beaten me to it. I'll leave this answer in place since I was the first to get all the numbers, my only mistake being to read "Add the number of easy pieces" as "Multiply by the number of easy pieces".

Multiply by the gables on Hawthorne's house. (7)
Add the number that a stitch in time saves. (9)
Add the number of blind mice. (3)
Subtract the number of William Pene du Bois' balloons. (21)
Add the number of wonders of the world. (7)
Subtract the number of miles in Camptown's racetrack. (5)
Subtract the number of strings on a violin. (4)
Divide by the number of vertices on a regular hexahedron. (8)
Add the number of the engine that ran on Chicago line. (9)
Multiply by the number of gentlemen of Verona. (2)
Add the atomic number of the element whose symbol is the 25th letter of the alphabet.(39)
Divide by the number of hills of Rome.(7)
Multiply by the number of railroads on a Monopoly board. (4)
Add the number of easy pieces. (5)
Add the number of chromosomes in a normal human muscle cell. (46)
Multiply by the number of kittens that lost their mittens. (3)
Add the number of acres in A.A.Milne's woods. (100)
Multiply by the number of cities in Dickens' tale. (2)
Subtract the number of degrees Fahrenheit at which . (451)
Add the number of Great Lakes. (5)
Divide by the number of days of the condor in the title of Grady's book. (6)
Subtract the number of blackbirds baked in a pie. (24)
Multiply by the number of horsemen of the Apocalypse. (4)
Divide by the number of men on a dead man's chest. (15)
Add the number of a neutral PH. (7)
Subtract the number of carbon atoms in a molecule of ethane. (2)
Multiply by the number of heads on Lofting's Push-me-Pull-you. (2)
Add the number of miles on the road sign to Juster's Digitopolis. (198)
Subtract the number of dried orange pips in a Sherlock Holmes case. (5)
Multiply by the number of the square at which Alice met Humpty Dumpty. (6)
Divide by the number of witches in Macbeth. (3)
Divide by the number of suits in a standard deck of cards.(4)

13*7+9+3-21+7-5-4/8+9*2+39/7*4+5+46*3+100*2-451+5/6-24*4/15+7-2+198-5*6/3/4
=>103