81920660 has 12 divisors (see below), whose sum is σ = 172033428. Its totient is φ = 32768256.

The previous prime is 81920653. The next prime is 81920689. The reversal of 81920660 is 6602918.

It can be written as a sum of positive squares in 2 ways, for example, as 23367556 + 58553104 = 4834^2 + 7652^2 .

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

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, 2047997 + ... + 2048036.

It is an arithmetic number, because the mean of its divisors is an integer number (14336119).

Almost surely, 2^81920660 is an apocalyptic number.

It is an amenable number.

81920660 is an abundant number, since it is smaller than the sum of its proper divisors (90112768).

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

81920660 is a wasteful number, since it uses less digits than its factorization.

81920660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4096042 (or 4096040 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 32.

The square root of 81920660 is about 9051.0032593078. The cubic root of 81920660 is about 434.3079850034.

The spelling of 81920660 in words is "eighty-one million, nine hundred twenty thousand, six hundred sixty".