82
82 is the atomic number of lead — the heaviest element with a stable isotope, and the origin of the word plumbing, from the Latin plumbum that Roman water pipes were made of.
- Even
- Composite
Where 82 fits
Why 82 is special
82's element marks a genuine boundary in the periodic table: nothing heavier than lead has a naturally stable isotope.
Same number, different meanings
How 82 is understood across different contexts — never implying one meaning because of another.
- Mathematics
82's element marks a genuine boundary in the periodic table: nothing heavier than lead has a naturally stable isotope.
- History
The English word plumbing comes from plumbum, the Latin name for element 82, because Roman water pipes were made of it — the same root gives the chemical symbol Pb and the plumb line. Roman engineers knew lead was harmful to the workers who smelted it; what they did not have was any way to connect chronic low-dose exposure to the water supply, and lead pipe remained standard in European and American plumbing into the twentieth century.
- Everyday life
Tetraethyl lead was added to petrol from the 1920s because it stopped engine knock cheaply, and the side effect was element 82 in the air of every city with traffic. Removing it took decades: the United States began phasing it out in 1975, the European Union completed its ban in 2000, and the last country stopped selling leaded petrol in 2021. Measured blood-lead levels fell sharply wherever the phase-out happened, which is why the episode is now a standard case study in how long a convenient additive can outlast the evidence against it.
- Science
82 is the atomic number of lead. Dense, soft and corrosion-resistant, it plumbed Roman cities and shielded X-ray rooms; recognition of its neurotoxicity has since removed it from paint, petrol and pipes.
82 is part of
Factors & digit properties
- Divisors (4)
- 1, 2, 41, 82
- Prime factorisation
- 2 × 41
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 82
- Scientific notation
- 8.200 × 10^1
Roman numerals
L X X X I I
Binary
1 0 1 0 0 1 0
1 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 1 × 2 + 0 × 1 = 82
Octal
1 2 2
1 × 64 + 2 × 8 + 2 × 1 = 82
Hexadecimal
5 2
5 × 16 + 2 × 1 = 82
Read as powers of two: 64 + 16 + 2 = 82.
In historical numeral systems
Egyptian
8 hobbles, 2 strokes
8 × 10 + 2 × 1 = 82. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 vertical wedge (sixties place), 2 corner wedges + 2 vertical wedges (units place)
1 × 60 + 22 = 82. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
pi, then beta, marked as a numeral
pi-beta + keraia
pi + beta written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
pe, then bet
pe-bet
pe (80) + bet (2) = 82, written in descending order.
Chinese numerals
bā shí èr
bā shí èr
八 before 十 multiplies it: 8 tens. 二 after it adds 2. The written form mirrors the arithmetic — "bā shí èr". The financial (anti-fraud) form is 捌拾貳.
Maya
4 dots (upper, twenties place) over 2 dots (lower, units place)
4 × 20 + 2 = 82. 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
- Happy number
- Semiprime
Related numbers & connections
41 is a factor of 82 (41 × 2 = 82).
View 41 →83 and 82 are consecutive integers.
View 83 →North and South Korea have separate calling codes and separate networks. Most North Korean mobile subscribers cannot place international calls at all, regardless of the code.
View 850 →History
The English word plumbing comes from plumbum, the Latin name for element 82, because Roman water pipes were made of it — the same root gives the chemical symbol Pb and the plumb line. Roman engineers knew lead was harmful to the workers who smelted it; what they did not have was any way to connect chronic low-dose exposure to the water supply, and lead pipe remained standard in European and American plumbing into the twentieth century.
DocumentedHistoryGeography: Roman Empire, later Europe and North AmericaPeriod: Roman era – 20th century
Everyday life
Tetraethyl lead was added to petrol from the 1920s because it stopped engine knock cheaply, and the side effect was element 82 in the air of every city with traffic. Removing it took decades: the United States began phasing it out in 1975, the European Union completed its ban in 2000, and the last country stopped selling leaded petrol in 2021. Measured blood-lead levels fell sharply wherever the phase-out happened, which is why the episode is now a standard case study in how long a convenient additive can outlast the evidence against it.
DocumentedEveryday lifeGeography: worldwide, phased out at different dates by countryPeriod: 1920s – 2021
Science
82 is the atomic number of lead. Dense, soft and corrosion-resistant, it plumbed Roman cities and shielded X-ray rooms; recognition of its neurotoxicity has since removed it from paint, petrol and pipes.
DocumentedScience
Mathematics
82 factors as 2 × 41.
DocumentedMathematics
Common questions
Why is plumbing called plumbing?
From plumbum, the Latin for lead — element 82 — because Roman water pipes were made of it. The same root gives lead its chemical symbol Pb and gives us the plumb line, a lead weight on a string. Lead pipe remained standard in European and American plumbing well into the twentieth century.
Is 82 a prime number?
No, 82 is not prime.
What are the factors of 82?
The factors of 82 are 1, 2, 41, 82.
What is 82 in Roman numerals?
82 in Roman numerals is LXXXII.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 4 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026