121809 has 8 divisors (see below), whose sum is σ = 171040. Its totient is φ = 76896.

The previous prime is 121789. The next prime is 121843. The reversal of 121809 is 908121.

121809 is nontrivially palindromic in base 16.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 121809 - 2⁸ = 121553 is a prime.

It is a Duffinian number.

121809 is a lucky number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 121809.

It is not an unprimeable number, because it can be changed into a prime (121889) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1012 + ... + 1125.

It is an arithmetic number, because the mean of its divisors is an integer number (21380).

2¹²¹⁸⁰⁹ is an apocalyptic number.

121809 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

121809 is a deficient number, since it is larger than the sum of its proper divisors (49231).

121809 is a wasteful number, since it uses less digits than its factorization.

121809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2159.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 121809 is about 349.0114611299. The cubic root of 121809 is about 49.5708606593.

The spelling of 121809 in words is "one hundred twenty-one thousand, eight hundred nine".