81091904209 has 8 divisors (see below), whose sum is σ = 81459106560. Its totient is φ = 80725260000.

The previous prime is 81091904203. The next prime is 81091904213. The reversal of 81091904209 is 90240919018.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 81091904209 - 2¹⁷ = 81091773137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81091904203) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 153084 + ... + 430834.

It is an arithmetic number, because the mean of its divisors is an integer number (10182388320).

Almost surely, 2^81091904209 is an apocalyptic number.

It is an amenable number.

81091904209 is a deficient number, since it is larger than the sum of its proper divisors (367202351).

81091904209 is a wasteful number, since it uses less digits than its factorization.

81091904209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279071.

The product of its (nonzero) digits is 46656, while the sum is 43.

The spelling of 81091904209 in words is "eighty-one billion, ninety-one million, nine hundred four thousand, two hundred nine".