18821409 has 8 divisors (see below), whose sum is σ = 25177152. Its totient is φ = 12506640.

The previous prime is 18821399. The next prime is 18821417. The reversal of 18821409 is 90412881.

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

It is not a de Polignac number, because 18821409 - 2⁹ = 18820897 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18821409.

It is not an unprimeable number, because it can be changed into a prime (18821449) 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, 9154 + ... + 11019.

It is an arithmetic number, because the mean of its divisors is an integer number (3147144).

Almost surely, 2^18821409 is an apocalyptic number.

It is an amenable number.

18821409 is a deficient number, since it is larger than the sum of its proper divisors (6355743).

18821409 is a wasteful number, since it uses less digits than its factorization.

18821409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20487.

The product of its (nonzero) digits is 4608, while the sum is 33.

The square root of 18821409 is about 4338.3647841093. The cubic root of 18821409 is about 266.0014745429.

The spelling of 18821409 in words is "eighteen million, eight hundred twenty-one thousand, four hundred nine".