81564396 has 12 divisors (see below), whose sum is σ = 190316952. Its totient is φ = 27188128.

The previous prime is 81564389. The next prime is 81564401. The reversal of 81564396 is 69346518.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3398505 + ... + 3398528.

It is an arithmetic number, because the mean of its divisors is an integer number (15859746).

Almost surely, 2^81564396 is an apocalyptic number.

It is an amenable number.

81564396 is an abundant number, since it is smaller than the sum of its proper divisors (108752556).

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

81564396 is a wasteful number, since it uses less digits than its factorization.

81564396 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6797040 (or 6797038 counting only the distinct ones).

The product of its digits is 155520, while the sum is 42.

The square root of 81564396 is about 9031.3009029707. The cubic root of 81564396 is about 433.6774841330.

The spelling of 81564396 in words is "eighty-one million, five hundred sixty-four thousand, three hundred ninety-six".