Ah, 96… the abstinent 69. 
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Golly, I wasn’t anticipating this many replies to a goofy new-topic reply 
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One never know what triggers people, one way or the reverse 
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Using the above fact to quickly convert multiples of 1/7 to decimal form is one of the tricks I use to establish my credibility as a maths teacher with impressionable students
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Look, there! 808!! Bob!!
I love all the answers, from “looks nice” upto high math and everything in-between.
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I’m adopting this. I don’t have a nickname. It doesn’t matter.
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My daughter actually told me that word, and once she did, the world made sense, at least for a few seconds.
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Seven, because of its significance in the Septimus Heap books- the seventh son of a seventh son, gifted with magical powers that make him the envy of fellow magicians. Funnily enough though, it was always his adoptive sister- Jenna, the small one without magic, but who lived by her wits and was passionate, loving, and loyal, who was my favourite. Also, she literally escaped being jailed by eating her way through a door she transformed into chocolate with a charm from her brother, which is genius, and hilarious. Her friendships are really heartwarming, and I admire her tenacity. Her and Beetle also made a cute couple later in the series. But seven is really significant in the books, (of which there are seven) and so I’ve grown a real fondness for it.
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I think I’ve been out done as a number nerd with the above mention of 163, which I confess I don’t understand what makes it special and the technical flew right over my head.
Anyways, some numbers I like:
3: only number that is both a Mersenne Prime and a Fermat Prime. Rule of 3. First triangular number.
7: first prime without a simple divisibility test in base 10, first double mersenne prime, first centered hexagonal number, the heptagon is the first regular polygon not constructible with compass and straight edge alone, ton of mystical stuff, go to number for macguffins that come in smallish sets, etc.
11: First repunit prime, first palindromic prime, number of sides of smallest regular polygon not constructible with compass, straightedge and angle trisector.
13: Mysticism that treats it as the anti-7, 13 rhomic dodecahedra forming the 3-d analog of 7 hexagons. first star number. There are 13 Archimedean and Catalan solids.
16: unique solution to x^y = y^x for x and y integers and x != y.
17 Fermat prime.
23: number of sides of smallest regular polygon not constructible with neusis.
36: First square triangular number.
37: First star hex number. 1/e is roughly 37% Another number with some mysticism attached.
42: The Answer to Life, the Universe, and Everything.
49: 7 squared.
91: 7*13, the first triangular hex number.
108: Another mystical number with some nice math properties.
120: Number of sides of largest fair die.
127: upper limit of a signed 8-bit integer. First Triple Mersenne prime.
216: 6 cubed, number of web safe colors.
257: Fermat Prime.
360: Degrees in a circle, smallest integer divisible by all integers 1-10 except 7.
666: Number of the beast, triangular number.
777: 3 * 7 * 37
1261: second Hex star number.
1337: Oldest nerd joke on the internet.
1440: Minutes in a day.
65537: Fermat Prime
16,777,216: number of colors in a 24-bit RGB colorspace. concatenation of 16, 777, and 216, see their entries above.
2^127 - 1: First quadruple Mersenne prime and only known quadruple mersenne prime.
2^(2^127 - 1) - 1 Candidate for first Quintuple Mersenne Prime, primality unknown and far beyond the size of the largest known prime.
Breaking away from integers, I’m a fan of the usual suspects such as phi, pi, tau, e, square roots of 2 and 3, cube root of 2, etc. Also a fan of the metallic means, n-nacci constants, and the golden trisection, which happens to be the lengths of the diagonals of a regular heptagon with unit edges.
Also, some of my favorite number words include myriad(10,000), milliard(a thousand million from the old British long scale, equal to the American short Billion that’s in common usage throughout the anglo-sphere these days), vigintillion(the 20th of the series that starts million, billion, trillion, 10^63 short sacle, 10^120 long scale), Goku(a japanese word for a large power of 10, but can’t remember which one and Google can’t give me a straight answer because of Dragon Ball and what articles I can find on large numbers in Japanese aren’t very screen reader friendly).
edit: a couple I forgot:
343: 7 cubed
7776: a perfect power one off from a repdigit. 7776 = 6^5.
Also, some kinda juvenile (dis?)honorable mentions:
69
420
8008 and 5138008
2110593
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Mmhm. 
On Threads there are so many “engagement bait” threads intended to garner tons of responses. It’s like benign sea-lioning. That was my (apparently too good) example/satire of one.
Other examples:
“I don’t use a rice cooker, why do I need one?”
“Do I really need an air fryer?”
“Hersheys is the best chocolate. This is not open for discussion.”
“Why drive 6 minutes for food when I can order doordash?”
“I don’t let my cat sleep on the bed with me. Is this a thing?”
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91 is the answer I give whenever anyone asks for my favourite prime, because it’s the only composite number less than 100 that can be reasonably mistaken for a prime (assuming that one can recognise multiples of 2, 3, 5, 11 and square numbers).
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In fact, probably the largest Fermat prime. It’s unknown whether there are any larger ones, and there are good reasons to believe there aren’t.
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Let’s see what mother nature thinks about my favourite number…
Magnesium! That’s a useful nutrient for our bodies. Alright, I can live with that.
8 is pretty important too. Oxygen is useful, I hear.
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Yes?
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Omg if you add 1 to one of my fav numbers, you get a Fermat Prime. This is wonderful news!
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Tangent: I loved the first few of those books, but I wish the author hadn’t committed so hard to the “seven” schtick, because I don’t think her story was really a natural fit for seven books. At some point it felt like she was completely overhauling her setting every book (“wait, why wasn’t this very important setting element ever mentioned before?”) because she’d run out of things to do with her existing lore.
…which is a very funny parallel to the whole “seventh son” thing in the books, where she almost immediately puts most of Septimus’s brothers on a bus to remove them from the plot, because it just made the family too big to work with.
Still, “the first books were so good that the series got extended too long and lost steam” is far from the worst complaint to have about a series! I still have the audiobook to Magyk in the family car for long drives.
(Those books are also responsible for part of my interest in typography, for making me go “huh, word processors treat bold and italic so similarly, but bold breaks up the flow of the text as I’m skimming a page and italics don’t, I wonder why that is?”)
As long as you’re not Grothendieck!
It’s also the largest prime I can remember, because I can never forget the powers of two that are relevant in computing!
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I had to Google this. That’s okay – I learned my multiplication tables a while ago.
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