28505709 has 16 divisors (see below), whose sum is σ = 43594240. Its totient is φ = 18390240.

The previous prime is 28505699. The next prime is 28505723. The reversal of 28505709 is 90750582.

28505709 is a `hidden beast` number, since 2 + 85 + 0 + 570 + 9 = 666.

It is not a de Polignac number, because 28505709 - 2¹¹ = 28503661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28505749) 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, 16192 + ... + 17865.

It is an arithmetic number, because the mean of its divisors is an integer number (2724640).

Almost surely, 2^28505709 is an apocalyptic number.

It is an amenable number.

28505709 is a deficient number, since it is larger than the sum of its proper divisors (15088531).

28505709 is a wasteful number, since it uses less digits than its factorization.

28505709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34097 (or 34091 counting only the distinct ones).

The product of its (nonzero) digits is 25200, while the sum is 36.

The square root of 28505709 is about 5339.0737960811. The cubic root of 28505709 is about 305.4761317218.

The spelling of 28505709 in words is "twenty-eight million, five hundred five thousand, seven hundred nine".