81604817680 has 20 divisors (see below), whose sum is σ = 189731201292. Its totient is φ = 32641927040.

The previous prime is 81604817633. The next prime is 81604817683. The reversal of 81604817680 is 8671840618.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 11229217024 + 70375600656 = 105968^2 + 265284^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (81604817683) 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 3 ways as a sum of consecutive naturals, for example, 510030031 + ... + 510030190.

Almost surely, 2^81604817680 is an apocalyptic number.

81604817680 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81604817680 is an abundant number, since it is smaller than the sum of its proper divisors (108126383612).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81604817680 is a wasteful number, since it uses less digits than its factorization.

81604817680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1020060234 (or 1020060228 counting only the distinct ones).

The product of its (nonzero) digits is 516096, while the sum is 49.

The spelling of 81604817680 in words is "eighty-one billion, six hundred four million, eight hundred seventeen thousand, six hundred eighty".