1808128909 has 4 divisors (see below), whose sum is σ = 1866455680. Its totient is φ = 1749802140.

The previous prime is 1808128871. The next prime is 1808128919. The reversal of 1808128909 is 9098218081.

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 a de Polignac number, because none of the positive numbers 2^k-1808128909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1808128919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29163339 + ... + 29163400.

It is an arithmetic number, because the mean of its divisors is an integer number (466613920).

Almost surely, 2^1808128909 is an apocalyptic number.

It is an amenable number.

1808128909 is a deficient number, since it is larger than the sum of its proper divisors (58326771).

1808128909 is an equidigital number, since it uses as much as digits as its factorization.

1808128909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58326770.

The product of its (nonzero) digits is 82944, while the sum is 46.

The square root of 1808128909 is about 42522.0990662502. The cubic root of 1808128909 is about 1218.2688222823.

The spelling of 1808128909 in words is "one billion, eight hundred eight million, one hundred twenty-eight thousand, nine hundred nine".