81635885618 has 36 divisors (see below), whose sum is σ = 144604865790. Its totient is φ = 34464431232.

The previous prime is 81635885609. The next prime is 81635885629. The reversal of 81635885618 is 81658853618.

It can be written as a sum of positive squares in only one way, i.e., 75791741809 + 5844143809 = 275303^2 + 76447^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 347138 + ... + 532706.

Almost surely, 2^81635885618 is an apocalyptic number.

81635885618 is a deficient number, since it is larger than the sum of its proper divisors (62968980172).

81635885618 is a wasteful number, since it uses less digits than its factorization.

81635885618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185719 (or 185645 counting only the distinct ones).

The product of its digits is 11059200, while the sum is 59.

The spelling of 81635885618 in words is "eighty-one billion, six hundred thirty-five million, eight hundred eighty-five thousand, six hundred eighteen".