81879864 has 64 divisors (see below), whose sum is σ = 224605440. Its totient is φ = 24668160.

The previous prime is 81879851. The next prime is 81879887. The reversal of 81879864 is 46897818.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50149 + ... + 51755.

It is an arithmetic number, because the mean of its divisors is an integer number (3509460).

Almost surely, 2^81879864 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81879864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112302720).

81879864 is an abundant number, since it is smaller than the sum of its proper divisors (142725576).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81879864 is a wasteful number, since it uses less digits than its factorization.

81879864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1820 (or 1816 counting only the distinct ones).

The product of its digits is 774144, while the sum is 51.

The square root of 81879864 is about 9048.7493058433. The cubic root of 81879864 is about 434.2358787706.

The spelling of 81879864 in words is "eighty-one million, eight hundred seventy-nine thousand, eight hundred sixty-four".