Number reference
29 explained.
29: twenty-nine, prime; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- twenty-nine
- Classification
- prime
- Factors
- 1, 29
- Prime factorization
- 29
- Square root
- 5.385165
- Cube root
- 3.072317
- Binary
- 11101
- Octal
- 35
- Hexadecimal
- 1D
- Roman numeral
- XXIX
- Digit sum
- 11
- Digital root
- 2
What makes 29 notable
- Prime. 29 is prime: it has exactly two divisors, 1 and itself, so it cannot be split into equal whole-number groups any other way.
29 in everyday use
Twenty-nine is the number of days in February in a leap year and the atomic number of copper. The synodic month — new moon to new moon — lasts about 29.5 days, which is why lunar calendars alternate months of 29 and 30 days. Saturn takes roughly 29.5 years to orbit the Sun, so a person sees Saturn return to the same patch of sky about once every three decades.
Twenty-nine is the tenth prime and the first of a twin pair with 31. It is the sum of two squares, 4 + 25, and a Pell number, appearing in the sequence 1, 2, 5, 12, 29 that gives ever-better fractions for the square root of two: 41/29 is accurate to three decimal places. It is also the sum of three consecutive squares, 4 + 9 + 16.
Nearby numbers
How to read this page
Because 29 is prime, the factor list stops at 1 and 29 itself, so it cannot be shared into equal whole-number groups. That is also what makes it useful as a building block: every larger number with 29 in its prime factorisation inherits it from here.
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