81562816717 has 4 divisors (see below), whose sum is σ = 81563674300. Its totient is φ = 81561959136.

The previous prime is 81562816669. The next prime is 81562816747. The reversal of 81562816717 is 71761826518.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 61968136356 + 19594680361 = 248934^2 + 139981^2 .

It is a cyclic number.

It is not a de Polignac number, because 81562816717 - 2¹⁵ = 81562783949 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 (81562816747) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 265368 + ... + 483265.

It is an arithmetic number, because the mean of its divisors is an integer number (20390918575).

Almost surely, 2^81562816717 is an apocalyptic number.

It is an amenable number.

81562816717 is a deficient number, since it is larger than the sum of its proper divisors (857583).

81562816717 is a wasteful number, since it uses less digits than its factorization.

81562816717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 857582.

The product of its digits is 1128960, while the sum is 52.

The spelling of 81562816717 in words is "eighty-one billion, five hundred sixty-two million, eight hundred sixteen thousand, seven hundred seventeen".