81664312 has 8 divisors (see below), whose sum is σ = 153120600. Its totient is φ = 40832152.

The previous prime is 81664259. The next prime is 81664321. The reversal of 81664312 is 21346618.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5104012 + ... + 5104027.

It is an arithmetic number, because the mean of its divisors is an integer number (19140075).

Almost surely, 2^81664312 is an apocalyptic number.

It is an amenable number.

81664312 is a deficient number, since it is larger than the sum of its proper divisors (71456288).

81664312 is a wasteful number, since it uses less digits than its factorization.

81664312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10208045 (or 10208041 counting only the distinct ones).

The product of its digits is 6912, while the sum is 31.

The square root of 81664312 is about 9036.8308604289. The cubic root of 81664312 is about 433.8544961632.

The spelling of 81664312 in words is "eighty-one million, six hundred sixty-four thousand, three hundred twelve".