28209805 has 16 divisors (see below), whose sum is σ = 36825264. Its totient is φ = 20620800.

The previous prime is 28209803. The next prime is 28209821. The reversal of 28209805 is 50890282.

It can be written as a sum of positive squares in 8 ways, for example, as 56169 + 28153636 = 237^2 + 5306^2 .

It is not a de Polignac number, because 28209805 - 2¹ = 28209803 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 (28209803) 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, 4417 + ... + 8713.

It is an arithmetic number, because the mean of its divisors is an integer number (2301579).

Almost surely, 2^28209805 is an apocalyptic number.

It is an amenable number.

28209805 is a deficient number, since it is larger than the sum of its proper divisors (8615459).

28209805 is a wasteful number, since it uses less digits than its factorization.

28209805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4416.

The product of its (nonzero) digits is 11520, while the sum is 34.

The square root of 28209805 is about 5311.2903328664. The cubic root of 28209805 is about 304.4154530096.

The spelling of 28209805 in words is "twenty-eight million, two hundred nine thousand, eight hundred five".