81318791809 has 8 divisors (see below), whose sum is σ = 85601480480. Its totient is φ = 77036378400.

The previous prime is 81318791779. The next prime is 81318791843. The reversal of 81318791809 is 90819781318.

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 81318791809 - 2⁷ = 81318791681 is a prime.

It is a super-2 number, since 2×81318791809² (a number of 23 digits) contains 22 as substring.

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 81318791809.

It is not an unprimeable number, because it can be changed into a prime (81318791909) 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 7 ways as a sum of consecutive naturals, for example, 857269 + ... + 947389.

It is an arithmetic number, because the mean of its divisors is an integer number (10700185060).

Almost surely, 2^81318791809 is an apocalyptic number.

It is an amenable number.

81318791809 is a deficient number, since it is larger than the sum of its proper divisors (4282688671).

81318791809 is a wasteful number, since it uses less digits than its factorization.

81318791809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137631.

The product of its (nonzero) digits is 870912, while the sum is 55.

The spelling of 81318791809 in words is "eighty-one billion, three hundred eighteen million, seven hundred ninety-one thousand, eight hundred nine".