47
47 is the atomic number of silver, which conducts electricity and heat better than any other element — copper wins on cost, not on performance. It is also the fifteenth prime.
- Odd
- Prime
Where 47 fits
Why 47 is special
47's ordinary primality is its main mathematical feature; its clearest real-world identity is as silver's atomic number.
47 connects to:
- 94 — is a factor of
Same number, different meanings
How 47 is understood across different contexts — never implying one meaning because of another.
- Mathematics
47's ordinary primality is its main mathematical feature; its clearest real-world identity is as silver's atomic number.
- Technology & computing
The largest single industrial use of element 47 is now solar photovoltaics: silver paste is screen-printed onto cells to carry the generated current off the wafer, and nothing else combines the conductivity with the required printability. Manufacturers have spent two decades reducing the grams per panel because the metal is a significant share of cell cost, which makes solar demand a genuine driver of the silver market.
- Science
Element 47 conducts electricity and heat better than any other element — better than copper, better than gold. It is not used for household wiring only because it is expensive and tarnishes, so copper wins on cost while silver is reserved for contacts, switch points, brazing alloys and printed conductive inks where the margin matters. Its tarnish is silver sulfide, not oxide, which is why silverware darkens near eggs and onions rather than in plain air.
- Media & popular culture
47 appears repeatedly across the modern Star Trek series as a deliberate writers' joke, introduced by producer Joe Menosky, who had encountered the 47 Society at Pomona College — a running campus claim that 47 occurs more often than chance allows. The number's frequency in the scripts is real and entirely intentional; the underlying claim about 47 in nature is a joke about confirmation bias.
47 is part of
Factors & digit properties
- Divisors (2)
- 1, 47
- Prime factorisation
- 47
- Digit sum
- 11
- Digital root
- 2
Representations
- Decimal
- 47
- Scientific notation
- 4.700 × 10^1
Roman numerals
X L V I I
XLVII uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 0 1 1 1 1
1 × 32 + 0 × 16 + 1 × 8 + 1 × 4 + 1 × 2 + 1 × 1 = 47
Octal
5 7
5 × 8 + 7 × 1 = 47
Hexadecimal
2 f
2 × 16 + f × 1 = 47
Read as powers of two: 32 + 8 + 4 + 2 + 1 = 47.
In historical numeral systems
Egyptian
4 hobbles, 7 strokes
4 × 10 + 7 × 1 = 47. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
4 corner wedges + 7 vertical wedges
47 fits in a single sexagesimal place: 4 corner wedges + 7 vertical wedges.
Greek (Ionic)
mu, then zeta, marked as a numeral
mu-zeta + keraia
mu + zeta written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
mem, then zayin
mem-zayin
mem (40) + zayin (7) = 47, written in descending order.
Chinese numerals
sì shí qī
sì shí qī
四 before 十 multiplies it: 4 tens. 七 after it adds 7. The written form mirrors the arithmetic — "sì shí qī". The financial (anti-fraud) form is 肆拾柒.
Maya
2 dots (upper, twenties place) over 1 bar + 2 dots (lower, units place)
2 × 20 + 7 = 47. Places stack vertically with the smallest at the bottom, so the upper group is worth twenty times the lower.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Deficient number
- Lucas number
- Safe prime
Related numbers & connections
47 is a factor of 94 (47 × 2 = 94).
View 94 →Mathematically related
- is a factor of94
why?
Strength 0.50, confidence "high".
Technology & computing
The largest single industrial use of element 47 is now solar photovoltaics: silver paste is screen-printed onto cells to carry the generated current off the wafer, and nothing else combines the conductivity with the required printability. Manufacturers have spent two decades reducing the grams per panel because the metal is a significant share of cell cost, which makes solar demand a genuine driver of the silver market.
DocumentedTechnology & computing
Science
Element 47 conducts electricity and heat better than any other element — better than copper, better than gold. It is not used for household wiring only because it is expensive and tarnishes, so copper wins on cost while silver is reserved for contacts, switch points, brazing alloys and printed conductive inks where the margin matters. Its tarnish is silver sulfide, not oxide, which is why silverware darkens near eggs and onions rather than in plain air.
DocumentedScience47 is the atomic number of silver, the best electrical and thermal conductor of any element. Before digital photography, silver halides were what made film and photographic paper light-sensitive.
DocumentedScience
Media & popular culture
47 appears repeatedly across the modern Star Trek series as a deliberate writers' joke, introduced by producer Joe Menosky, who had encountered the 47 Society at Pomona College — a running campus claim that 47 occurs more often than chance allows. The number's frequency in the scripts is real and entirely intentional; the underlying claim about 47 in nature is a joke about confirmation bias.
DocumentedMedia & popular cultureGeography: United States
Mathematics
47 is prime — the 15th prime number — sitting directly before the perfect square 49.
DocumentedMathematics
Common questions
If silver conducts best, why is wiring made of copper?
Cost, almost entirely. Silver beats copper by only a few per cent in conductivity and costs many times more, so the margin never justifies it for bulk wiring. Silver is used where the small gain matters and the quantity is tiny — contacts, switch points, brazing alloys, conductive inks.
Why does 47 keep appearing in Star Trek?
Because the writers put it there. Producer Joe Menosky brought the habit from Pomona College, whose 47 Society jokes that the number turns up more often than chance allows. The frequency in the scripts is deliberate; the underlying claim is a joke about noticing what you look for.
Is 47 a prime number?
Yes, 47 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 47?
The factors of 47 are 1, 47.
What is 47 in Roman numerals?
47 in Roman numerals is XLVII. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be XXXXVII, which Roman inscriptions used freely — the strict subtractive form is a later convention.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 5 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026