I prefer pi

Okay, so we didn’t get many takers with our last DDC-number-as-interesting-sequence-of-digits post, but we’re undeterred and we’re going to soldier on with this thread. Remember the idea was to find the number that includes the longest possible sequence of the same single digit, and hopefully it would beat the best that we could come up with at the time, which was 333.333 (sale and gift of land). Giles found what he claimed to be the longest possible sequence of 9s (745.6199999 for calligraphy of artificial languages), but five 9s doesn’t beat six 3s. Then, in a previously unreported feat of number-building nimbleness, Winton came up not only with record-equaling 277.7777, 347.77777, and 633.3333 (for, respectively, Christianity and the Christian church in Fremont County, Iowa; the civil procedure and courts of Fremont County; and the propagation, from suckers, runners, or buds, of cowpeas), but also with the current champ: 266.66666, missions of the Disciples of Christ in Liberia and Côte d’Ivoire. That’s, uh, seven 6s. But now we’d like to shift gears a little. Last Friday’s nifty DDC number of the day was 121 -- a humble example of the palindrome, reading the same whether you begin on the left or on the right. It’s quite short, though, isn’t it? 786.87, for concussion idiophones, is a little more respectable, but hardly impressive. Even good ol’ 333.333 beats that. Got any longer ones? Like, really long?

Comments

[Will]

The best I've managed so far (and I hope these are all valid numbers) are:

631.494136 - Soil studies in East Lothian, Scotland
726.909627 - Other buildings for religious purposes in Darfur
741.595147 - Collections of cartoons from Qinghai Province, China

But there must be longer ones built from Table 2 with -909- in the middle

[Giles Martin]

I've gone through the printed schedules (not literally, but in electronic form), and the longest palindromes there (ignoring the decimal point) are:
342.0243 -- Other convention documents
615.8516 -- Bibliotherapy and educational therapies
621.3126 -- Modification and storage

(And a very bibliotherapeutic and educational exercise this is, too!)