Number reference
99 explained.
99: ninety-nine, composite, repdigit; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- ninety-nine
- Classification
- composite
- Factors
- 1, 3, 9, 11, 33, 99
- Prime factorization
- 3 × 3 × 11
- Square root
- 9.949874
- Cube root
- 4.626065
- Binary
- 1100011
- Octal
- 143
- Hexadecimal
- 63
- Roman numeral
- XCIX
- Digit sum
- 18
- Digital root
- 9
What makes 99 notable
- Repdigit. 99 is written with a single repeated digit, so it is divisible by the repunit of the same length.
99 in everyday use
Ninety-nine cents is the classic price ending, chosen because shoppers read $9.99 as closer to nine dollars than ten. Wayne Gretzky wore 99 through his career and the NHL retired the number league-wide in 2000. Nena's "99 Luftballons" was a worldwide hit in 1983, and "99 Bottles of Beer" is the long-form counting song. Ninety-nine is the atomic number of einsteinium, first identified in the debris of a 1952 hydrogen-bomb test.
Ninety-nine is 9 × 11, a repdigit, and one less than a hundred. It is a Kaprekar number: 99² = 9,801, and 98 + 01 = 99. Its reciprocal is 0.010101…, which is why any two-digit number divided by 99 simply repeats: 37/99 = 0.373737…. In binary it is 1100011, and it is the largest two-digit number.
Nearby numbers
How to read this page
The factor list shows every way 99 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 99 for contexts that do not use decimal.
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