The smallest prime whose reciprocal contains a period that is exactly 1/3 of the maximum length. [Wells]
Illinois has two area codes that are multiples of 103: 309 (3 * 103) and 618 (6 * 103). [Litman]
Proof, an award-winning play by David Auburn, revolves around a mysterious mathematical proof involving prime numbers left behind in 103 notebooks by a young woman's brilliant father.
The world's largest tree is the General Sherman Tree, a sequoia in Sequoia National Park, California. Its trunk is roughly 103 feet in circumference. [Jolly]
3 and 103 are prime, as are 3*2^103-1 and 103*2^3-1. There is no other pair of primes less than 1000 with this property. [Hartley]
103 + (10!)^3 is prime. [Patterson]
M103 and NGC 103 are both open clusters of stars in Cassiopeia. [Necula]
Astronomer Charles Messier cataloged 103 objects in his list of nebulae. [McCranie]
The smallest positive integer with no double-base representation of length 2. (Vassil S. Dimitrov, Everett W. Howe, Lower bounds on the lengths of double-base representations, January 23, 2010). [Post]
103 is the sum of the second digits of all two-digit primes. [Silva]
The prime with a partition into prime parts using the most distinct digits: 103 = 2 + 5 + 7 + 89. [Beedassy]
The book 103 Mathematical Curiosities: Theory of Numbers, Figures and Relationships in Contemporary Mathematics by Pietro Paolo Lava and Giorgio Balzarotti deals with 103 short monographic chapters on various topics of mathematics concerning the theory of numbers.
A 116252718750, B 126549297400319587938067556680330478718512220, C 20194901948267217839018728287420415124151392820360, D 833143468021550307316406250000, E 1602302009605762500000, F 5051690607024954179010179893239071469494516923352311358251857714821860897146935224605560302734375000000, G 52754204988843750000000, H 18478269411645510070000708007812500000000, I 67939538643524160000, J 1312736671231405826729030115169078090910076550483224710581928719180917750000000000, K 46723126600104034500000000000, L 688905000000000000, M 132324872400000000000, N 8125874138560062910137743601493047743667635427563822773710937500000000000000, O 185280690471924772779927545401344000, P 210000000000000000, Q 74284098949096853302886400000, R 322366034239817959383642175680000000000000, S 3795662919494318722708025280474805080475238400000, T 66050754992353410652665600000000000000, U 10723890009193816615419130183121829604565018053348609927956523266048000000000, V 386805489821561152262500957843301996383380003645661756342665216000, W 749052176126504624234060514486543964496375917554490041332742511040151552000000000, X 43583638688782314429699855241539747840, Y 72645686886652946011545600000000000000, Z 95724945709235937630308342513664000000000000.
(There is one curio for this number that has not yet been approved by an editor.)