81645684 has 12 divisors (see below), whose sum is σ = 190506624. Its totient is φ = 27215224.

The previous prime is 81645677. The next prime is 81645761. The reversal of 81645684 is 48654618.

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

It is a congruent number.

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, 3401892 + ... + 3401915.

It is an arithmetic number, because the mean of its divisors is an integer number (15875552).

Almost surely, 2^81645684 is an apocalyptic number.

It is an amenable number.

81645684 is an abundant number, since it is smaller than the sum of its proper divisors (108860940).

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

81645684 is a wasteful number, since it uses less digits than its factorization.

81645684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6803814 (or 6803812 counting only the distinct ones).

The product of its digits is 184320, while the sum is 42.

The square root of 81645684 is about 9035.8001305916. The cubic root of 81645684 is about 433.8215055951.

The spelling of 81645684 in words is "eighty-one million, six hundred forty-five thousand, six hundred eighty-four".