One hundred fifty-three has two genuinely separate claims to notability — one purely mathematical, one historical and textual — that happen to attach to the identical value for entirely unrelated reasons, making it a useful case study in how a number can be "famous" along completely independent tracks at once.
The mathematical property is being what's called a narcissistic number (also known as an Armstrong number, after the mathematician who first formally described the concept): the sum of each of its digits, each raised to the power equal to the total number of digits in the number, equals the number itself. For 153, a three-digit number: 1³ + 5³ + 3³ = 1 + 125 + 27 = 153, exactly. This isn't approximately true or a rounding coincidence — it's an exact equality, verifiable by hand in under a minute, and 153 is one of only four three-digit narcissistic numbers in base 10 (the others being 370, 371, and 407) — a genuinely small, specific, checkable family.
Narcissistic numbers get progressively rarer relative to the total count of numbers as the digit count grows, because the sum of digit-powers grows much more slowly than the numbers themselves once you get past a certain digit length — which is exactly why narcissistic numbers of any given digit-length form a small, finite, fully enumerable set rather than an infinite family, a genuinely interesting structural fact in its own right within recreational number theory.
The separate, textual claim to fame comes from the New Testament, specifically John 21:11, which recounts a scene in which the disciples, following Jesus's instruction, cast a net and haul in a catch described precisely as 153 large fish — a specific numerical detail that has drawn extensive theological and numerological commentary across centuries of biblical scholarship, given how unusual it is for a New Testament narrative to include such a precise, seemingly arbitrary count. Interpretations proposed over the centuries have ranged from symbolic readings connecting 153 to the sum of all integers from 1 to 17 (153 is, in fact, the 17th triangular number: T(17) = 17×18÷2 = 153, a genuine and checkable mathematical fact about the same number) to broader claims about it representing the totality of nations or peoples known to the ancient world in some early Christian numerological schemes. No single interpretation of the passage's specific number has achieved universal scholarly consensus, and it's worth being honest that the text itself does not explain why 153 specifically was recorded — later commentators have supplied various proposed meanings without a definitive resolution from the source material itself.
What makes 153 a genuinely interesting case for this site specifically is that its status as a triangular number (T(17)=153) is a real, provable mathematical fact that some biblical commentators have specifically invoked when discussing the passage — meaning the mathematical and textual stories about this number aren't entirely disconnected coincidences the way, say, 42's factorization and its fictional fame are; some genuine historical interpretive traditions have explicitly drawn the connection between 153's mathematical structure and its scriptural context, even though the connection itself remains a matter of interpretation rather than settled fact.
It's worth being explicit about the boundary between these two stories, since they're easy to blur together carelessly: the narcissistic-number property is a fully rigorous, mechanically checkable mathematical fact, true regardless of any interpretive tradition. The connection to the Gospel passage, and any symbolic reading built on top of 153's mathematical properties, belongs to the separate domain of textual and theological interpretation, where reasonable scholars can and do disagree. Treating both as real, genuine, and worth knowing — while being clear about which kind of "true" each one is — is the more accurate way to hold the whole picture.
370 and 371, the two narcissistic numbers immediately following 153 in the base-10 sequence, are worth checking by hand as a quick follow-up exercise once 153's own verification feels comfortable: 3³+7³+0³=27+343+0=370, and 3³+7³+1³=27+343+1=371 — both landing exactly on themselves, the same exact property, verified with the same short arithmetic, on two entirely different three-digit values.
407, the fourth and final three-digit narcissistic number, rounds out the complete set: 4³+0³+7³=64+0+343=407. Beyond three digits, narcissistic numbers become considerably rarer relative to the surrounding numbers, and the complete set at each digit length is fully known and finite, a satisfying, fully closed piece of recreational number theory in contrast to some of the genuinely open questions covered elsewhere on this site.