815586661 has 4 divisors (see below), whose sum is σ = 815736492. Its totient is φ = 815436832.

The previous prime is 815586643. The next prime is 815586683. The reversal of 815586661 is 166685518.

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 169156036 + 646430625 = 13006^2 + 25425^2 .

It is a cyclic number.

It is not a de Polignac number, because 815586661 - 2¹¹ = 815584613 is a prime.

It is a super-2 number, since 2×815586661² = 1330363203202257842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (815586641) 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, 66430 + ... + 77743.

It is an arithmetic number, because the mean of its divisors is an integer number (203934123).

Almost surely, 2^815586661 is an apocalyptic number.

It is an amenable number.

815586661 is a deficient number, since it is larger than the sum of its proper divisors (149831).

815586661 is a wasteful number, since it uses less digits than its factorization.

815586661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149830.

The product of its digits is 345600, while the sum is 46.

The square root of 815586661 is about 28558.4779181244. The cubic root of 815586661 is about 934.3079366952.

The spelling of 815586661 in words is "eight hundred fifteen million, five hundred eighty-six thousand, six hundred sixty-one".