Number reference
75 explained.
75: seventy-five, composite; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- seventy-five
- Classification
- composite
- Factors
- 1, 3, 5, 15, 25, 75
- Prime factorization
- 3 × 5 × 5
- Square root
- 8.660254
- Cube root
- 4.217163
- Binary
- 1001011
- Octal
- 113
- Hexadecimal
- 4B
- Roman numeral
- LXXV
- Digit sum
- 12
- Digital root
- 3
What makes 75 notable
- Factor structure. 75 breaks down into 2 distinct primes (3, 5) and has 6 divisors in total, so it can be split into equal whole-number groups 4 ways beyond 1 and itself.
75 in everyday use
Seventy-five is the atomic number of rhenium, one of the rarest metals in the Earth's crust, used in jet-engine alloys. A seventy-fifth anniversary is diamond, and 75 percent is three quarters. The 75 mm gun was the standard field piece of the French army in 1914 and gave its name to the French 75 cocktail. In France, a postcode beginning 75 means Paris.
Seventy-five is 3 × 5² and the sum of three equal squares, 25 + 25 + 25. It is a Keith number: start with its digits 7 and 5, keep adding the last two terms, and the sequence 7, 5, 12, 17, 29, 46, 75 returns to the number itself. It is also a pentagonal pyramidal number, following 1, 6, 18, and 40. In binary it is 1001011.
Nearby numbers
How to read this page
The factor list shows every way 75 splits into equal whole-number groups — 6 divisors in total. The prime factorisation is the compact form of that same information, and the base conversions restate 75 for contexts that do not use decimal.
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