81640797500 has 30 divisors (see below), whose sum is σ = 178532101440. Its totient is φ = 32656318000.

The previous prime is 81640797487. The next prime is 81640797509. The reversal of 81640797500 is 579704618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81640797509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 16325660 + ... + 16330659.

It is an arithmetic number, because the mean of its divisors is an integer number (5951070048).

Almost surely, 2^81640797500 is an apocalyptic number.

It is an amenable number.

81640797500 is an abundant number, since it is smaller than the sum of its proper divisors (96891303940).

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

81640797500 is a wasteful number, since it uses less digits than its factorization.

81640797500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32656343 (or 32656326 counting only the distinct ones).

The product of its (nonzero) digits is 423360, while the sum is 47.

The spelling of 81640797500 in words is "eighty-one billion, six hundred forty million, seven hundred ninety-seven thousand, five hundred".