81771205618 has 16 divisors (see below), whose sum is σ = 123566522040. Its totient is φ = 40582434816.

The previous prime is 81771205603. The next prime is 81771205631. The reversal of 81771205618 is 81650217718.

It can be written as a sum of positive squares in 4 ways, for example, as 19364670649 + 62406534969 = 139157^2 + 249813^2 .

It is an unprimeable number.

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, 4186018 + ... + 4205506.

Almost surely, 2^81771205618 is an apocalyptic number.

81771205618 is a deficient number, since it is larger than the sum of its proper divisors (41795316422).

81771205618 is a wasteful number, since it uses less digits than its factorization.

81771205618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34941.

The product of its (nonzero) digits is 188160, while the sum is 46.

The spelling of 81771205618 in words is "eighty-one billion, seven hundred seventy-one million, two hundred five thousand, six hundred eighteen".