81819564 has 12 divisors (see below), whose sum is σ = 190912344. Its totient is φ = 27273184.

The previous prime is 81819523. The next prime is 81819593. The reversal of 81819564 is 46591818.

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

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, 3409137 + ... + 3409160.

It is an arithmetic number, because the mean of its divisors is an integer number (15909362).

Almost surely, 2^81819564 is an apocalyptic number.

It is an amenable number.

81819564 is an abundant number, since it is smaller than the sum of its proper divisors (109092780).

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

81819564 is a wasteful number, since it uses less digits than its factorization.

81819564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6818304 (or 6818302 counting only the distinct ones).

The product of its digits is 69120, while the sum is 42.

The square root of 81819564 is about 9045.4167399850. The cubic root of 81819564 is about 434.1292556742.

The spelling of 81819564 in words is "eighty-one million, eight hundred nineteen thousand, five hundred sixty-four".