Number reference
169 explained.
169: one hundred sixty-nine, composite, perfect square; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- one hundred sixty-nine
- Classification
- composite
- Factors
- 1, 13, 169
- Prime factorization
- 13 × 13
- Square root
- 13
- Cube root
- 5.528775
- Binary
- 10101001
- Octal
- 251
- Hexadecimal
- A9
- Roman numeral
- CLXIX
- Digit sum
- 16
- Digital root
- 7
What makes 169 notable
- Perfect square. 169 = 13², so a square of side 13 has an area of 169.
169 in everyday use
One hundred sixty-nine is thirteen squared, and it is the square in the best-known Pythagorean triple after 3-4-5: 5² + 12² = 13², so a right triangle with legs 5 and 12 has a hypotenuse of 13. Carpenters and surveyors have used the 5-12-13 rule for centuries to lay out right angles with a knotted rope. In Roman numerals it is CLXIX, and a 169-square grid, thirteen by thirteen, is the board size of some traditional games.
The number has a mirror trick: reverse its digits to get 961, and that is 31², the square of 13 reversed. Only a few pairs behave this way, 12² = 144 and 21² = 441 being the other small example. It is also a Pell number, appearing in the sequence 1, 2, 5, 12, 29, 70, 169 that gives the best rational approximations to the square root of two, and a Markov number, one of the solutions to x² + y² + z² = 3xyz, in the triple 2, 29, 169.
Nearby numbers
How to read this page
The factor list shows every way 169 splits into equal whole-number groups — 3 divisors in total. The prime factorisation is the compact form of that same information, and the base conversions restate 169 for contexts that do not use decimal.
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