Some years ago I produced a little PDF on Figurate Numbers, which I have continued to expand over the years in various forms. It is now coming together under the title "Numberlore" which as the name suggests covers a much wider range of topics.
Recently I have come across this website: Numbers Aplenty which includes lists of numerous classes of numbers that I have not come across before. Some seem rather trivial, but others are interesting..
Another website I've long been familiar with is Math Day of the Year Facts: Number Facts for Every Year Day ((1-30)) from "On This Day in Math" which has a similar eclectic selection of properties of numbers.
I would be interested to learn of other websites of this nature. The Numberphile pages on YouTube are another source of miscellaneous number lore. Also the Online Encyclopedia of Integer Sequences (OEIS).
My main interest is in whole numbers rather than irrationals, though they are of course related and turn up as limits of ratios of whole number terms in sequences.
A curious book on numbers with a rather bombastic title is Numbers, Their Occult Power and Mystic Virtues by W. Wynn Westcott (1911) but its mathematical content is disappointing. The subject being mainly the occurrence of numbers in Bible texts and commentaries.
