81439684335785 has 4 divisors (see below), whose sum is σ = 97727621202948. Its totient is φ = 65151747468624.

The previous prime is 81439684335733. The next prime is 81439684335791. The reversal of 81439684335785 is 58753348693418.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 45753684637609 + 35685999698176 = 6764147^2 + 5973776^2 .

It is a cyclic number.

It is not a de Polignac number, because 81439684335785 - 2¹⁸ = 81439684073641 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8143968433574 + ... + 8143968433583.

It is an arithmetic number, because the mean of its divisors is an integer number (24431905300737).

Almost surely, 2^{81439684335785} is an apocalyptic number.

It is an amenable number.

81439684335785 is a deficient number, since it is larger than the sum of its proper divisors (16287936867163).

81439684335785 is a wasteful number, since it uses less digits than its factorization.

81439684335785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16287936867162.

The product of its digits is 2090188800, while the sum is 74.

The spelling of 81439684335785 in words is "eighty-one trillion, four hundred thirty-nine billion, six hundred eighty-four million, three hundred thirty-five thousand, seven hundred eighty-five".