1) If population growth continues at the same rate (1.1%) then we will have used all the particles in the known universe within the next 8,604 years

It's hard to believe. There are not enough particles in the visible universe to support the rate if human growth for more than 8,604 years. This number doesn't even take into account other types of life on our planet and possible other planets. This was a figure recently calculated on Numberphile by Tony Padilla.

2) The sum of all natural numbers (1+2+3+4+5...) is equal to -1/12

This is a bit of a controversial one. It's a bit of a counter-intuitive idea. The proof is...strange? To say the least but it does work. Check out the proof for yourself, again from Numberphile and let me know what you think.

3) A Googol (1 with 100 zeroes after it) is a larger than the number of particles in the universe

It is also where Google got their famous name from. A Googolplex is written as 1 with a googol number of zeroes after it. There is literally not enough space in the universe to write down the number in it's long form. It is just too large.

4) If you stretch out all of the DNA in your body you would have enough to reach Pluto and back 17 times over

Why would you not want to?

5) The number 0.999... is the same as writing 1

This carries one of the quickest proofs I have ever seen.
N = 0.999...
100N = 99.999... 99N=99 N=1 0.999... = 1

6) You can fit all of the other planets in our solar system between the Earth and the Moon

Providing you take the distance where the Moon is at it's farthest from us then you can fit every single planet in the gap if you were to place them pole-to-pole.

7) The coldest any substance can be is -273.15 C

Otherwise known as absolute zero this is the lowest temperature that any substance or object can reach. This is because the atoms have no energy at this point, meaning it is impossible to lose any more energy (heat). Absolute zero is set at 0 in the Kelvin scale and equates to -459.67 F.

8) The sum of any 3 consecutive numbers is divisible by 3

For example: 3+4+5 = 12 which is divisible by 3. The same also works for the sum of any 5 consecutive numbers being divisible by 5.

9) Venus is the only planet to spin in the opposite direction to Earth

It also takes 243 days to rotate, the longest in the solar system. This makes a day on Venus longer than a year on Venus (225 days).

10) If someone is asked to pick a number between 1 and 10 chances are they will pick 7.

This is because they wouldn't choose 1 or 10 cause that's too obvious. 5 is in the middle so that's out. it's not going to be an even number so 2,4,6 and 8 are gone, leaving 3 and 7. 3 is too small of a number so 7 takes the gold.