81665388 has 48 divisors (see below), whose sum is σ = 241973760. Its totient is φ = 23332752.

The previous prime is 81665383. The next prime is 81665411. The reversal of 81665388 is 88356618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81665383) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53256 + ... + 54767.

It is an arithmetic number, because the mean of its divisors is an integer number (5041120).

Almost surely, 2^81665388 is an apocalyptic number.

It is an amenable number.

81665388 is an abundant number, since it is smaller than the sum of its proper divisors (160308372).

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

81665388 is a wasteful number, since it uses less digits than its factorization.

81665388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108043 (or 108035 counting only the distinct ones).

The product of its digits is 276480, while the sum is 45.

The square root of 81665388 is about 9036.8903943779. The cubic root of 81665388 is about 433.8564016279.

The spelling of 81665388 in words is "eighty-one million, six hundred sixty-five thousand, three hundred eighty-eight".