81608765 has 12 divisors (see below), whose sum is σ = 113919516. Its totient is φ = 55960128.

The previous prime is 81608759. The next prime is 81608777. The reversal of 81608765 is 56780618.

It can be written as a sum of positive squares in 2 ways, for example, as 54848836 + 26759929 = 7406^2 + 5173^2 .

It is not a de Polignac number, because 81608765 - 2¹⁶ = 81543229 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

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 11 ways as a sum of consecutive naturals, for example, 166304 + ... + 166793.

It is an arithmetic number, because the mean of its divisors is an integer number (9493293).

Almost surely, 2^81608765 is an apocalyptic number.

It is an amenable number.

81608765 is a deficient number, since it is larger than the sum of its proper divisors (32310751).

81608765 is a wasteful number, since it uses less digits than its factorization.

81608765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333116 (or 333109 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 41.

The square root of 81608765 is about 9033.7569703861. The cubic root of 81608765 is about 433.7561064620.

The spelling of 81608765 in words is "eighty-one million, six hundred eight thousand, seven hundred sixty-five".