81166401 has 16 divisors (see below), whose sum is σ = 124126720. Its totient is φ = 52364880.

The previous prime is 81166391. The next prime is 81166433. The reversal of 81166401 is 10466118.

81166401 is a `hidden beast` number, since 8 + 1 + 16 + 640 + 1 = 666.

It is not a de Polignac number, because 81166401 - 2¹⁰ = 81165377 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81166441) 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, 47650 + ... + 49323.

It is an arithmetic number, because the mean of its divisors is an integer number (7757920).

Almost surely, 2^81166401 is an apocalyptic number.

It is an amenable number.

81166401 is a deficient number, since it is larger than the sum of its proper divisors (42960319).

81166401 is a wasteful number, since it uses less digits than its factorization.

81166401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97013 (or 97007 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 81166401 is about 9009.2397570494. The cubic root of 81166401 is about 432.9709545700.

The spelling of 81166401 in words is "eighty-one million, one hundred sixty-six thousand, four hundred one".