81380664 has 24 divisors (see below), whose sum is σ = 220406160. Its totient is φ = 27126864.

The previous prime is 81380659. The next prime is 81380681. The reversal of 81380664 is 46608318.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (36).

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 in 5 ways as a sum of consecutive naturals, for example, 565072 + ... + 565215.

It is an arithmetic number, because the mean of its divisors is an integer number (9183590).

Almost surely, 2^81380664 is an apocalyptic number.

It is an amenable number.

81380664 is an abundant number, since it is smaller than the sum of its proper divisors (139025496).

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

81380664 is a wasteful number, since it uses less digits than its factorization.

81380664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1130299 (or 1130292 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 81380664 is about 9021.1232116627. The cubic root of 81380664 is about 433.3516052782.

The spelling of 81380664 in words is "eighty-one million, three hundred eighty thousand, six hundred sixty-four".