81694787329 has 3 divisors (see below), whose sum is σ = 81695073153. Its totient is φ = 81694501506.

The previous prime is 81694787327. The next prime is 81694787341. The reversal of 81694787329 is 92378749618.

The square root of 81694787329 is 285823.

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

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 is not a de Polignac number, because 81694787329 - 2¹ = 81694787327 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81694787323) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 142912 + ... + 428734.

It is an arithmetic number, because the mean of its divisors is an integer number (27231691051).

Almost surely, 2^81694787329 is an apocalyptic number.

81694787329 is the 285823-rd square number.

81694787329 is the 142912-nd centered octagonal number.

It is an amenable number.

81694787329 is a deficient number, since it is larger than the sum of its proper divisors (285824).

81694787329 is an frugal number, since it uses more digits than its factorization.

81694787329 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 571646 (or 285823 counting only the distinct ones).

The product of its digits is 36578304, while the sum is 64.

Multiplying 81694787329 by its sum of digits (64), we get a square (5228466389056 = 2286584²).

The spelling of 81694787329 in words is "eighty-one billion, six hundred ninety-four million, seven hundred eighty-seven thousand, three hundred twenty-nine".