There are infinitely many kinds of infinities in mathematics. Although there are infinitely many measurable numbers between every two integers, there are as many integers as natural numbers. This is because there is a bijection between these sets. This infinity is the smallest of the infinities and is called a countable infinity. The real or complex numbers, on the other hand, are much more numerous — that is, recalculable infinity. ¹⁾

Both IV and IIII are correct forms of writing the Roman numeral four. In ancient times, Roman numerals were written differently and much less consistently than today. Nowadays, the number four is usually written IV, but not always — in the case of clock faces it is common to write four as IIII. This tradition has a practical reason: thanks to it, the number IV is not mistaken for VI, especially when the watch is taken out of the pocket and held upside down. ²⁾

Centillion is the number 10 to the power of 600. The power indicates how many zeros there are after the one (not the number ten), and this is true in each case. Accordingly, 10 to the power of 42 is the number one septillion, 10 to the power of 48 is the number one octillion and 10 to the power of 100 is the number one googol. In this number, the same rule applies (with zeros) as with the number one centillion. ³⁾

In 1967, the Polish mathematician Sierpinski and Selfridge postulated that 78,557 is the smallest Sierpinski number. To prove this, it must be shown that all odd numbers smaller than 78,557 are not Sierpinski numbers. As of 2007, there are only six numbers that have not been ruled out as possible Sierpinski numbers and can solve the problem. ⁴⁾

“The Divine Comedy”, written by Dante in 1308-1321, is a triptych: It consists of three books with each book consisting of 33 songs for a total of 99 songs. The introductory song makes a total of 100. Each of the songs is written in tercinea, a three-verse stanza. The key number three is a symbol of the Holy Trinity and the number 100 symbolizes perfection. ⁵⁾