Thirty

A little change this time and, to mark this the 30th birthday of my Jonathan, some facts about the number 30.

A polygon with thirty sides is a triacontagon. Adding all the internal angles, each of 168 degrees, totals 5040 degrees.

There are thirty major and minor keys in music.

It is a Harshad number, or a number divisible by the sum of its digits. Also known as a Niven number, the term Harshad was coined by D. R. Kaprekar and comes from the Sanskrit harsa 'joy' and give 'give and thus 'to give joy', while the alternative Niven Number remembers a paper delivered by Canadian-born mathematician Ivan M. Niven in 1977.

There are thirty upright stones forming the Sarsen Circle at Stonehenge.

Cats have just 30 teeth, 16 in the upper jaw and 14 in the lower.

In binary code 11110 is thirty, in French trente, Basque Hogeita hamar, Bosnian trideset, Catalan trenta, Croatian trideset, Danish tredive, Dutch dertig, Hungarian harminc, Irish triocha, Italian trenta, Norwegian tretti, Portuguese trinta, Romanian treizeci, Slovenian trideset, Spanish treinta, Swedish trettio, and Welsh deg ar hugain.

The 30th wedding anniversary is the Pearl Anniversary. Originally only silver and gold were marked, a tradition coming from Roman times, but over the years all manner of oddities have been added.

The atomic number of zinc is 30. It is the fourth most commonly used metal - after iron, aluminium and copper - over 50% of which is used as a rust-proof coating. It has been said to help prevent the common cold, although the side effects of bad breath and nausea may be worse than the cold itself.

The 30th November is Computer Security Day. Beginning in 1988 it is when computer vulnerabilities are highlighted.

The 30th president of the United States of America was Calvin Coolidge, the 30th UK prime minister was William Lamb serving his second term from 1835 to 1841.

A recent list of the world's richest people listed Elon Musk at number 30 with a net worth of $22.8 billion.

In area the 30th largest country in the world in Egypt, but by population that ranking goes to Spain.

The 30th person in space was Richard Gordon on Gemini 11, launched 12th September 1966. Like Michael Collins before him, he was the one left in orbit around the moon when the other two went for a walk on the Apollo 12 mission.

The 30th football club to win the English title were Liverpool, the 30th FA Cup Final Nottingham Forest, and the 30th League Cup Final Nottingham Forest.