813605665 has 4 divisors (see below), whose sum is σ = 976326804. Its totient is φ = 650884528.

The previous prime is 813605641. The next prime is 813605671. The reversal of 813605665 is 566506318.

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 502118464 + 311487201 = 22408^2 + 17649^2 .

It is a cyclic number.

It is not a de Polignac number, because 813605665 - 2⁹ = 813605153 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 81360562 + ... + 81360571.

It is an arithmetic number, because the mean of its divisors is an integer number (244081701).

Almost surely, 2^813605665 is an apocalyptic number.

It is an amenable number.

813605665 is a deficient number, since it is larger than the sum of its proper divisors (162721139).

813605665 is a wasteful number, since it uses less digits than its factorization.

813605665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162721138.

The product of its (nonzero) digits is 129600, while the sum is 40.

The square root of 813605665 is about 28523.7736809140. The cubic root of 813605665 is about 933.5508698578.

It can be divided in two parts, 81360 and 5665, that added together give a square (87025 = 295²).

The spelling of 813605665 in words is "eight hundred thirteen million, six hundred five thousand, six hundred sixty-five".