28408815891 has 12 divisors (see below), whose sum is σ = 41989258168. Its totient is φ = 18498763584.

The previous prime is 28408815881. The next prime is 28408815899. The reversal of 28408815891 is 19851880482.

28408815891 is a `hidden beast` number, since 28 + 408 + 81 + 58 + 91 = 666.

It is not a de Polignac number, because 28408815891 - 2¹¹ = 28408813843 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28408815899) 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, 36703510 + ... + 36704283.

Almost surely, 2^28408815891 is an apocalyptic number.

28408815891 is a deficient number, since it is larger than the sum of its proper divisors (13580442277).

28408815891 is a wasteful number, since it uses less digits than its factorization.

28408815891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73407842 (or 73407839 counting only the distinct ones).

The product of its (nonzero) digits is 1474560, while the sum is 54.

The spelling of 28408815891 in words is "twenty-eight billion, four hundred eight million, eight hundred fifteen thousand, eight hundred ninety-one".