81665968 has 10 divisors (see below), whose sum is σ = 158227844. Its totient is φ = 40832976.

The previous prime is 81665963. The next prime is 81665981. The reversal of 81665968 is 86956618.

It is not an unprimeable number, because it can be changed into a prime (81665963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2552046 + ... + 2552077.

Almost surely, 2^81665968 is an apocalyptic number.

It is an amenable number.

81665968 is a deficient number, since it is larger than the sum of its proper divisors (76561876).

81665968 is a wasteful number, since it uses less digits than its factorization.

81665968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5104131 (or 5104125 counting only the distinct ones).

The product of its digits is 622080, while the sum is 49.

The square root of 81665968 is about 9036.9224850056. The cubic root of 81665968 is about 433.8574287302.

The spelling of 81665968 in words is "eighty-one million, six hundred sixty-five thousand, nine hundred sixty-eight".