29 (number)

29 (twenty-nine) is the natural number following 28 and preceding 30. It is a prime number.

29 is the number of days February has on a leap year.

29 is the tenth prime number.

29 is the fifth primorial prime, like its twin prime 31.

29 is the smallest positive whole number that cannot be made from the numbers ${\displaystyle \{1,2,3,4\}}$, using each digit exactly once and using only addition, subtraction, multiplication, and division. None of the first twenty-nine natural numbers have more than two different prime factors (in other words, this is the longest such consecutive sequence; the first sphenic number or triprime, 30 is the product of the first three primes 2, 3, and 5). 29 is also,

On the other hand, 29 represents the sum of the first cluster of consecutive semiprimes with distinct prime factors (14, 15). These two numbers are the only numbers whose arithmetic mean of divisors is the first perfect number and unitary perfect number, 6 (that is also the smallest semiprime with distinct factors). The pair (14, 15) is also the first floor and ceiling values of imaginary parts of non-trivial zeroes in the Riemann zeta function, ${\displaystyle \zeta .}$

29 is the largest prime factor of the smallest number with an abundancy index of 3,

It is also the largest prime factor of the smallest abundant number not divisible by the first even (of only one) and odd primes, 5391411025 = 5² × 7 × 11 × 13 × 17 × 19 × 23 × 29. Both of these numbers are divisible by consecutive prime numbers ending in 29.