28166391 has 12 divisors (see below), whose sum is σ = 44383560. Its totient is φ = 17070480.

The previous prime is 28166381. The next prime is 28166407. The reversal of 28166391 is 19366182.

28166391 is a `hidden beast` number, since 2 + 8 + 16 + 639 + 1 = 666.

It is not a de Polignac number, because 28166391 - 2¹¹ = 28164343 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28166371) 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, 142156 + ... + 142353.

It is an arithmetic number, because the mean of its divisors is an integer number (3698630).

Almost surely, 2^28166391 is an apocalyptic number.

28166391 is a deficient number, since it is larger than the sum of its proper divisors (16217169).

28166391 is a wasteful number, since it uses less digits than its factorization.

28166391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 284526 (or 284523 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 28166391 is about 5307.2018050947. The cubic root of 28166391 is about 304.2592109052.

The spelling of 28166391 in words is "twenty-eight million, one hundred sixty-six thousand, three hundred ninety-one".