81665001 has 12 divisors (see below), whose sum is σ = 128684400. Its totient is φ = 49493880.

The previous prime is 81664967. The next prime is 81665011. The reversal of 81665001 is 10056618.

81665001 is a `hidden beast` number, since 8 + 1 + 6 + 650 + 0 + 1 = 666.

It is not a de Polignac number, because 81665001 - 2¹⁰ = 81663977 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81665011) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 412351 + ... + 412548.

It is an arithmetic number, because the mean of its divisors is an integer number (10723700).

Almost surely, 2^81665001 is an apocalyptic number.

It is an amenable number.

81665001 is a deficient number, since it is larger than the sum of its proper divisors (47019399).

81665001 is a wasteful number, since it uses less digits than its factorization.

81665001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 824916 (or 824913 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 81665001 is about 9036.8689821199. The cubic root of 81665001 is about 433.8557163001.

The spelling of 81665001 in words is "eighty-one million, six hundred sixty-five thousand, one".