805636661 has 4 divisors (see below), whose sum is σ = 808771692. Its totient is φ = 802501632.

The previous prime is 805636639. The next prime is 805636739. The reversal of 805636661 is 166636508.

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 420496036 + 385140625 = 20506^2 + 19625^2 .

It is a cyclic number.

It is not a de Polignac number, because 805636661 - 2⁶ = 805636597 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 (805636561) 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, 1567130 + ... + 1567643.

It is an arithmetic number, because the mean of its divisors is an integer number (202192923).

Almost surely, 2^805636661 is an apocalyptic number.

It is an amenable number.

805636661 is a deficient number, since it is larger than the sum of its proper divisors (3135031).

805636661 is a wasteful number, since it uses less digits than its factorization.

805636661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3135030.

The product of its (nonzero) digits is 155520, while the sum is 41.

The square root of 805636661 is about 28383.7393766220. The cubic root of 805636661 is about 930.4929213358.

The spelling of 805636661 in words is "eight hundred five million, six hundred thirty-six thousand, six hundred sixty-one".