81876561689 has 4 divisors (see below), whose sum is σ = 88174758756. Its totient is φ = 75578364624.

The previous prime is 81876561671. The next prime is 81876561709. The reversal of 81876561689 is 98616567818.

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 32073944464 + 49802617225 = 179092^2 + 223165^2 .

It is a cyclic number.

It is not a de Polignac number, because 81876561689 - 2³² = 77581594393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81876561629) 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, 3149098514 + ... + 3149098539.

It is an arithmetic number, because the mean of its divisors is an integer number (22043689689).

Almost surely, 2^81876561689 is an apocalyptic number.

It is an amenable number.

81876561689 is a deficient number, since it is larger than the sum of its proper divisors (6298197067).

81876561689 is a wasteful number, since it uses less digits than its factorization.

81876561689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6298197066.

The product of its digits is 34836480, while the sum is 65.

The spelling of 81876561689 in words is "eighty-one billion, eight hundred seventy-six million, five hundred sixty-one thousand, six hundred eighty-nine".