37
37 is a prime number, the atomic number of rubidium, and the traditional reference figure (in Celsius) for normal human body temperature.
- Odd
- Prime
Where 37 fits
Why 37 is special
37°C's familiarity as 'normal' body temperature obscures how much real individual variation is actually healthy.
Same number, different meanings
How 37 is understood across different contexts — never implying one meaning because of another.
- Mathematics
37°C's familiarity as 'normal' body temperature obscures how much real individual variation is actually healthy.
- History
37°C entered medicine through Carl Reinhold August Wunderlich, whose 1868 work recorded something over a million readings from around 25,000 patients and established both the average and the idea that fever is a measurable sign rather than a disease in itself. Modern re-analyses put the average slightly lower, and one study has argued human body temperature has genuinely fallen since the nineteenth century rather than merely being measured better.
- Science
There are roughly 37 trillion cells in an adult human body (adults, an order-of-magnitude estimate). Cell-count estimates vary substantially with method; this is the commonly cited figure from a 2013 review.
- Everyday life
37°C (98.6°F) is the traditional reference figure for normal human body temperature, though real individual variation of roughly half a degree either way is normal and healthy.
37 is part of
Factors & digit properties
- Divisors (2)
- 1, 37
- Prime factorisation
- 37
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 37
- Scientific notation
- 3.700 × 10^1
Roman numerals
X X X V I I
Binary
1 0 0 1 0 1
1 × 32 + 0 × 16 + 0 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 37
Octal
4 5
4 × 8 + 5 × 1 = 37
Hexadecimal
2 5
2 × 16 + 5 × 1 = 37
Read as powers of two: 32 + 4 + 1 = 37.
In historical numeral systems
Egyptian
3 hobbles, 7 strokes
3 × 10 + 7 × 1 = 37. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 corner wedges + 7 vertical wedges
37 fits in a single sexagesimal place: 3 corner wedges + 7 vertical wedges.
Greek (Ionic)
lambda, then zeta, marked as a numeral
lambda-zeta + keraia
lambda + zeta written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
lamed, then zayin
lamed-zayin
lamed (30) + zayin (7) = 37, written in descending order.
Chinese numerals
sān shí qī
sān shí qī
三 before 十 multiplies it: 3 tens. 七 after it adds 7. The written form mirrors the arithmetic — "sān shí qī". The financial (anti-fraud) form is 參拾柒.
Maya
1 dot (upper, twenties place) over 3 bars + 2 dots (lower, units place)
1 × 20 + 17 = 37. 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
- Lucky number (mathematical sieve)
Related numbers & connections
37 is a factor of 74 (37 × 2 = 74).
View 74 →The televised claim turns on seventy-three being the twenty-first prime and its reversal the twelfth.
View 73 →History
37°C entered medicine through Carl Reinhold August Wunderlich, whose 1868 work recorded something over a million readings from around 25,000 patients and established both the average and the idea that fever is a measurable sign rather than a disease in itself. Modern re-analyses put the average slightly lower, and one study has argued human body temperature has genuinely fallen since the nineteenth century rather than merely being measured better.
DocumentedHistoryPeriod: 1868
Science
There are roughly 37 trillion cells in an adult human body (adults, an order-of-magnitude estimate). Cell-count estimates vary substantially with method; this is the commonly cited figure from a 2013 review.
DocumentedScienceGeography: adults, an order-of-magnitude estimate37 is the atomic number of rubidium. Rubidium atomic clocks are the compact, affordable tier of precision timekeeping, common in telecommunications networks and satellite equipment.
DocumentedScience
Everyday life
37°C (98.6°F) is the traditional reference figure for normal human body temperature, though real individual variation of roughly half a degree either way is normal and healthy.
Widely documentedEveryday life
Mathematics
111 is 3 x 37, so every three-digit repdigit — 111, 222, 333 and the rest — is divisible by 37. It follows that any three-digit number whose digits are rotated, such as 148, 481 and 814, keeps 37 as a factor if it had one.
DocumentedMathematics
Common questions
Is 37°C really normal body temperature?
It is a nineteenth-century average that has stuck. Carl Wunderlich's 1868 study of some 25,000 patients produced 37°C, and later work puts the modern average slightly lower, nearer 36.6°C. Healthy temperature also varies by roughly half a degree with the person, the time of day and where it is measured — an oral reading and a rectal one are not the same number.
Why is 111 divisible by 37?
Because 111 = 3 × 37. That makes every three-digit repdigit — 222, 333, 444 and the rest — divisible by 37 as well, since each is 111 times a digit. It also means rotating the digits of a multiple of 37 gives another one: 148, 481 and 814 are all divisible by 37.
Is 37 a prime number?
Yes, 37 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 37?
The factors of 37 are 1, 37.
What is 37 in Roman numerals?
37 in Roman numerals is XXXVII.
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