81668089 has 4 divisors (see below), whose sum is σ = 84484260. Its totient is φ = 78851920.

The previous prime is 81668077. The next prime is 81668113. The reversal of 81668089 is 98086618.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 44555625 + 37112464 = 6675^2 + 6092^2 .

It is a cyclic number.

It is not a de Polignac number, because 81668089 - 2⁹ = 81667577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81668189) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1408042 + ... + 1408099.

It is an arithmetic number, because the mean of its divisors is an integer number (21121065).

Almost surely, 2^81668089 is an apocalyptic number.

It is an amenable number.

81668089 is a deficient number, since it is larger than the sum of its proper divisors (2816171).

81668089 is a wasteful number, since it uses less digits than its factorization.

81668089 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2816170.

The product of its (nonzero) digits is 165888, while the sum is 46.

The square root of 81668089 is about 9037.0398361410. The cubic root of 81668089 is about 433.8611846955.

The spelling of 81668089 in words is "eighty-one million, six hundred sixty-eight thousand, eighty-nine".