805409208661 has 4 divisors (see below), whose sum is σ = 805414882924. Its totient is φ = 805403534400.

The previous prime is 805409208649. The next prime is 805409208677. The reversal of 805409208661 is 166802904508.

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 221454948100 + 583954260561 = 470590^2 + 764169^2 .

It is a cyclic number.

It is not a de Polignac number, because 805409208661 - 2⁵ = 805409208629 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 (805409203661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2618610 + ... + 2909971.

It is an arithmetic number, because the mean of its divisors is an integer number (201353720731).

Almost surely, 2^805409208661 is an apocalyptic number.

It is an amenable number.

805409208661 is a deficient number, since it is larger than the sum of its proper divisors (5674263).

805409208661 is a wasteful number, since it uses less digits than its factorization.

805409208661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5674262.

The product of its (nonzero) digits is 829440, while the sum is 49.

The spelling of 805409208661 in words is "eight hundred five billion, four hundred nine million, two hundred eight thousand, six hundred sixty-one".