81680522729 has 4 divisors (see below), whose sum is σ = 87963639876. Its totient is φ = 75397405584.

The previous prime is 81680522723. The next prime is 81680522741. The reversal of 81680522729 is 92722508618.

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 3884156329 + 77796366400 = 62323^2 + 278920^2 .

It is a cyclic number.

It is not a de Polignac number, because 81680522729 - 2⁴ = 81680522713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81680522723) 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, 3141558554 + ... + 3141558579.

It is an arithmetic number, because the mean of its divisors is an integer number (21990909969).

Almost surely, 2^81680522729 is an apocalyptic number.

It is an amenable number.

81680522729 is a deficient number, since it is larger than the sum of its proper divisors (6283117147).

81680522729 is a wasteful number, since it uses less digits than its factorization.

81680522729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6283117146.

The product of its (nonzero) digits is 967680, while the sum is 50.

The spelling of 81680522729 in words is "eighty-one billion, six hundred eighty million, five hundred twenty-two thousand, seven hundred twenty-nine".