19818809 has 4 divisors (see below), whose sum is σ = 20069760. Its totient is φ = 19567860.

The previous prime is 19818797. The next prime is 19818811. The reversal of 19818809 is 90881891.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 19818809 - 2⁴ = 19818793 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19818809.

It is not an unprimeable number, because it can be changed into a prime (19818899) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 125357 + ... + 125514.

It is an arithmetic number, because the mean of its divisors is an integer number (5017440).

Almost surely, 2^19818809 is an apocalyptic number.

It is an amenable number.

19818809 is a deficient number, since it is larger than the sum of its proper divisors (250951).

19818809 is an equidigital number, since it uses as much as digits as its factorization.

19818809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250950.

The product of its (nonzero) digits is 41472, while the sum is 44.

The square root of 19818809 is about 4451.8320947673. The cubic root of 19818809 is about 270.6195603093.

The spelling of 19818809 in words is "nineteen million, eight hundred eighteen thousand, eight hundred nine".