81729089689 has 9 divisors (see below), whose sum is σ = 88503571359. Its totient is φ = 75438806040.

The previous prime is 81729089623. The next prime is 81729089707. The reversal of 81729089689 is 98698092718.

The square root of 81729089689 is 285883.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 12090102025 + 69638987664 = 109955^2 + 263892^2 .

It is not a de Polignac number, because 81729089689 - 2²¹ = 81726992537 is a prime.

It is a super-2 number, since 2×81729089689² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81729089609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3705484 + ... + 3727474.

It is an arithmetic number, because the mean of its divisors is an integer number (9833730151).

Almost surely, 2^81729089689 is an apocalyptic number.

81729089689 is the 285883-rd square number.

81729089689 is the 142942-nd centered octagonal number.

It is an amenable number.

81729089689 is a deficient number, since it is larger than the sum of its proper divisors (6774481670).

81729089689 is an frugal number, since it uses more digits than its factorization.

81729089689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44008 (or 22004 counting only the distinct ones).

The product of its (nonzero) digits is 31352832, while the sum is 67.

The spelling of 81729089689 in words is "eighty-one billion, seven hundred twenty-nine million, eighty-nine thousand, six hundred eighty-nine".