81568820 has 12 divisors (see below), whose sum is σ = 171294564. Its totient is φ = 32627520.

The previous prime is 81568819. The next prime is 81568849. The reversal of 81568820 is 2886518.

It can be written as a sum of positive squares in 2 ways, for example, as 49056016 + 32512804 = 7004^2 + 5702^2 .

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, 2039201 + ... + 2039240.

It is an arithmetic number, because the mean of its divisors is an integer number (14274547).

Almost surely, 2^81568820 is an apocalyptic number.

It is an amenable number.

81568820 is an abundant number, since it is smaller than the sum of its proper divisors (89725744).

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

81568820 is a wasteful number, since it uses less digits than its factorization.

81568820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4078450 (or 4078448 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 38.

The square root of 81568820 is about 9031.5458256048. The cubic root of 81568820 is about 433.6853247865.

The spelling of 81568820 in words is "eighty-one million, five hundred sixty-eight thousand, eight hundred twenty".