We tend to think of odd numbers as male and even numbers as female.

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This ancient belief was tested by James Wilkie and Galen Bodenhausen of Northwestern University. In his latest book, Alex Bellos writes: "They showed respondents randomly assigned pictures of the faces of young babies, each next to a three-digit number that was either odd-odd-odd or even-even-even, and asked them to guess the baby’s sex [...] Respondents were about 10 per cent more likely to say that a baby paired with odd numbers was a boy, than if the same baby was paired with even numbers."

. If you shuffle a pack of cards properly, chances are that exact order has never been seen before in the whole history of the universe.

Via giphy.com

Proof.

 Zero is an even number.

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But people take longer to decide whether it's even or odd because it's not as easy for us to mentally categorise.

 There's not enough space in the known universe to write out a googolplex on paper.

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According to Carl Sagan in the original Cosmos series. A googolplex is 10 to the power of a googol, or 10 to the power of 10 to the power of 100. This website will write it out for you (or start... it won't ever finish because your computer won't have enough memory).

The most popular favourite number is 7.

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Flickr: losmininos / Creative Commons

Nearly 3000 people, around 10% of the total asked, chose 7 as their favourite number in an online poll by Alex Bellos. The second most popular was 3.