In the Greek alphabet, p is the 16^{th} letter (and 16 is the square of 4). In the English alphabet, p is also the 16^{th} letter, and I is the 9^{th} letter (the square of 3). Add them up (16 +9), and you get 25 (the square of 5). Multiply them (16 x 9), and you get 144 (the square of 12), divide 9/16, and you get .5625 (the square of .75). It’s no wonder that they say, “ Pi are squared.

Pi is the number of times a circle's diameter will fit around its circumference.

Most people would say that a circle has no corners, but it is more accurate to say that it has an infinite number of corners.

The sequences of digits in Pi have so far passed all known tests for randomness.

Here are the first 100 decimal places of Pi

3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679

The fraction (22 / 7) is a well-used number for Pi. It is accurate to 0.04025%.

Another fraction used as an approximation to Pi is (355 / 113) which is accurate to 0.00000849%

A more accurate fraction of Pi is (104348 / 33215). This is accurate to 0.00000001056%.

Pi occurs in hundreds of equations in many sciences including those describing the DNA double helix, a rainbow, ripples spreading from where a raindrop fell into water, general relativity, geometry problems, waves, etc.

There is no zero in the first 31 digits of Pi.

Pi is irrational. An irrational number is a number that cannot be expressed as a ratio of integers.

In 1991, the Chudnovsky brothers in New York, using their computer, m zero, calculated pi to two billion two hundred sixty million three hundred twenty one thousand three hundred sixty three digits (2, 260, 321, 363). They halted the program that summer.

The Pi memory champion is Hiroyoki Gotu, who memorized an amazing 42,000 digits.

The old memory champion was Hideaki Tomoyori, born Sep. 30, 1932. In Yokohama, Japan, Hideaki recited pi from memory to 40,000 places in 17 hrs. 21 min. including breaks totaling 4 hrs. 15min. on 9-10 of March in 1987 at the Tsukuba University Club House.

Pi is of course the ratio of a circle's circumference to its diameter. If you bring everything up one dimension to get 3D value for Pi, the ratio of a sphere's surface area to the area of the circle seen if you cut the sphere in half is exactly 4.

If you take 10 million random digits, statistically on average you would expect 200 cases where you get 5 digits in a row the same. If you take 10 million digits of Pi, you get exactly 200.

If a billion decimals of pi were printed in ordinary type, they would stretch from New York City, to the middle of Kansas.

The square root of 9.869604401 is approximately Pi. The square root of an irrational number is irrational too.

For a circle to equal pi the diameter must be 1.

In 1949 it took ENIAC (Electronic Numerical Integrator and Computer) 70 hours to calculate 2,037 decimal places of Pi.

By the year 1701 the first 100 digits of pi had been calculated.

In 1706 William Jones first gave the Greek letter " p" its current mathematical definition.

In 1768 Johann Lambert proved Pi is irrational.

Simon Plouffe was listed in the 1975 Guinness Book of World Records for reciting 4096 digits of Pi from memory.

In 1897 the State House of Representatives of Indiana unanimously passed a bill setting pi equal to 16/(sqrt 3), which approximately equals 9.2376!

Taking the first 6,000,000,000 decimal places of Pi, this is the distribution:

0 occurs 599,963,005 times,

1 occurs 600,033,260 times,

2 occurs 599,999,169 times,

3 occurs 600,000,243 times,

4 occurs 599,957,439 times,

5 occurs 600,017,176 times,

6 occurs 600,016,588 times,

7 occurs 600,009,044 times,

8 occurs 599,987,038 times,

9 occurs 600,017,038 times.

This shows NO unusual deviation from expected 'random' behavior.

Half the circumference of a circle with radius 1 is exactly Pi. The area inside that circle is also exactly Pi!

It is impossible to 'square the circle'. I.e.: You can't draw a square with the same area as a circle using standard / Euclidean straightedge and compass construction in a finite number of steps. The Greeks were obsessed with trying to do this.

The volume of a sphere is 4/3 pr3 and its surface area is 4pr2.

At position 763 there are six nines in a row. This is known as the Feynman Point

Write the letters of the English alphabet, in capitals, clockwise around a circle, and cross out the letters that have right-left symmetry, A, H, I, M, etc. The letters that remain group themselves in sets of 3, 1, 4, 1, 6"

Pi day is celebrated on March 14 at the Exploratorium in San Francisco (March 14 is 3/14) at 1:59 PST, which is 3.14159.

Here's a Pi limerick:

Three point one four one five nine two

It’s been around forever - its not new

It appears everywhere in here and in there

Its irrational I know but its true!