85815209 has 4 divisors (see below), whose sum is σ = 86391300. Its totient is φ = 85239120.

The previous prime is 85815199. The next prime is 85815211. The reversal of 85815209 is 90251858.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14784025 + 71031184 = 3845^2 + 8428^2 .

It is a cyclic number.

It is not a de Polignac number, because 85815209 - 2⁴ = 85815193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (85815239) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 287822 + ... + 288119.

It is an arithmetic number, because the mean of its divisors is an integer number (21597825).

Almost surely, 2^85815209 is an apocalyptic number.

It is an amenable number.

85815209 is a deficient number, since it is larger than the sum of its proper divisors (576091).

85815209 is a wasteful number, since it uses less digits than its factorization.

85815209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 576090.

The product of its (nonzero) digits is 28800, while the sum is 38.

The square root of 85815209 is about 9263.6498746444. The cubic root of 85815209 is about 441.0841189934.

The spelling of 85815209 in words is "eighty-five million, eight hundred fifteen thousand, two hundred nine".