81565933080997 has 4 divisors (see below), whose sum is σ = 81566051692140. Its totient is φ = 81565814469856.

The previous prime is 81565933080851. The next prime is 81565933081007. The reversal of 81565933080997 is 79908033956518.

It is a Cunningham number, because it is equal to 9031386²+1.

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 80246373145156 + 1319559935841 = 8958034^2 + 1148721^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81565933080997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81565933180997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 58268008 + ... + 59651425.

It is an arithmetic number, because the mean of its divisors is an integer number (20391512923035).

Almost surely, 2^{81565933080997} is an apocalyptic number.

It is an amenable number.

81565933080997 is a deficient number, since it is larger than the sum of its proper divisors (118611143).

81565933080997 is a wasteful number, since it uses less digits than its factorization.

81565933080997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118611142.

The product of its (nonzero) digits is 440899200, while the sum is 73.

The spelling of 81565933080997 in words is "eighty-one trillion, five hundred sixty-five billion, nine hundred thirty-three million, eighty thousand, nine hundred ninety-seven".