This number is a prime.
Illinois has two area codes that are multiples of 103: 309 (3 * 103) and 618 (6 * 103). [Litman]
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.
The only prime that can be represented in four ways as sum of a double-digit prime plus the reversal of another double-digit prime, i.e., 11+R(29), 29+R(47), 71+R(23), 89+R(41). [Loungrides]
103 is the smallest prime not found in the first thousand digits of π. These digits of π count the initial digit "3" and 999 decimal digits. Note that the same applies to the prime 107 while the prime 109 already appears in the first thousand digits of π. [Rivera]
There are 103 species of beetle native to the Indonesian island of Sulawesi. [Homewood]