81287728879 has 4 divisors (see below), whose sum is σ = 92900261584. Its totient is φ = 69675196176.

The previous prime is 81287728877. The next prime is 81287728891. The reversal of 81287728879 is 97882778218.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81287728879 - 2¹ = 81287728877 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 (81287728877) 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, 5806266342 + ... + 5806266355.

It is an arithmetic number, because the mean of its divisors is an integer number (23225065396).

Almost surely, 2^81287728879 is an apocalyptic number.

81287728879 is a deficient number, since it is larger than the sum of its proper divisors (11612532705).

81287728879 is a wasteful number, since it uses less digits than its factorization.

81287728879 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11612532704.

The product of its digits is 50577408, while the sum is 67.

The spelling of 81287728879 in words is "eighty-one billion, two hundred eighty-seven million, seven hundred twenty-eight thousand, eight hundred seventy-nine".