Number reference
45 explained.
45: forty-five, composite, triangular number; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- forty-five
- Classification
- composite
- Factors
- 1, 3, 5, 9, 15, 45
- Prime factorization
- 3 × 3 × 5
- Square root
- 6.708204
- Cube root
- 3.556893
- Binary
- 101101
- Octal
- 55
- Hexadecimal
- 2D
- Roman numeral
- XLV
- Digit sum
- 9
- Digital root
- 9
What makes 45 notable
- Triangular number. 45 is the 9th triangular number: it is the sum 1 + 2 + … + 9, the count of items in a triangle with 9 rows.
45 in everyday use
Forty-five degrees is half a right angle, the angle of an even diagonal, and the slope at which rise equals run.
Nearby numbers
How to read this page
The factor list shows every way 45 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 45 for contexts that do not use decimal.
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