81659966 has 8 divisors (see below), whose sum is σ = 123614040. Its totient is φ = 40455288.

The previous prime is 81659947. The next prime is 81659971. The reversal of 81659966 is 66995618.

It is a sphenic number, since it is the product of 3 distinct primes.

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 3 ways as a sum of consecutive naturals, for example, 187076 + ... + 187511.

It is an arithmetic number, because the mean of its divisors is an integer number (15451755).

Almost surely, 2^81659966 is an apocalyptic number.

81659966 is a deficient number, since it is larger than the sum of its proper divisors (41954074).

81659966 is a wasteful number, since it uses less digits than its factorization.

81659966 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 374698.

The product of its digits is 699840, while the sum is 50.

The square root of 81659966 is about 9036.5903968256. The cubic root of 81659966 is about 433.8467997573.

The spelling of 81659966 in words is "eighty-one million, six hundred fifty-nine thousand, nine hundred sixty-six".