Number reference
120 explained.
120: one hundred twenty, composite, factorial; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- one hundred twenty
- Classification
- composite
- Factors
- 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120
- Prime factorization
- 2 × 2 × 2 × 3 × 5
- Square root
- 10.954451
- Cube root
- 4.932424
- Binary
- 1111000
- Octal
- 170
- Hexadecimal
- 78
- Roman numeral
- CXX
- Digit sum
- 3
- Digital root
- 3
What makes 120 notable
- Factorial. 120 = 5! — the product of every whole number from 1 to 5. It counts the ways 5 distinct items can be put in order.
- Triangular number. 120 is the 15th triangular number: it is the sum 1 + 2 + … + 15, the count of items in a triangle with 15 rows.
- Highly composite. 120 has 16 divisors — more than any smaller positive number. That is why numbers like this get chosen for units of time, angle, and packaging.
120 in everyday use
One hundred twenty is five factorial, the number of ways to arrange five distinct items in order. The Babylonians, counting in sixties, treated it as twice their base, and in Germanic tradition a "great hundred" was 120 rather than 100. It survives in photography as 120 film, the medium-format roll introduced by Kodak in 1901 and still manufactured, and in displays as a 120 Hz refresh rate. Each interior angle of a regular hexagon is 120 degrees, the reason honeycomb cells meet three at a corner.
It is exceptionally divisible: sixteen divisors, more than any smaller number, which makes it a highly composite number and explains why it was useful for trade and for dividing a circle. It is also the fifteenth triangular number, 1 + 2 + … + 15, and the eighth tetrahedral number, so 120 cannonballs stack into a perfect tetrahedron. Its abundance is striking too: the proper divisors of 120 add up to 240, twice the number itself.
Nearby numbers
How to read this page
The factor list shows every way 120 splits into equal whole-number groups — 16 divisors in total. The prime factorisation is the compact form of that same information, and the base conversions restate 120 for contexts that do not use decimal.
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