3665605561 has 4 divisors (see below), whose sum is σ = 3674747124. Its totient is φ = 3656464000.

The previous prime is 3665605487. The next prime is 3665605579. The reversal of 3665605561 is 1655065663.

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 3420495225 + 245110336 = 58485^2 + 15656^2 .

It is a cyclic number.

It is not a de Polignac number, because 3665605561 - 2²⁷ = 3531387833 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3665605591) 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, 4570180 + ... + 4570981.

It is an arithmetic number, because the mean of its divisors is an integer number (918686781).

Almost surely, 2^3665605561 is an apocalyptic number.

It is an amenable number.

3665605561 is a deficient number, since it is larger than the sum of its proper divisors (9141563).

3665605561 is an equidigital number, since it uses as much as digits as its factorization.

3665605561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9141562.

The product of its (nonzero) digits is 486000, while the sum is 43.

The square root of 3665605561 is about 60544.2446562842. The cubic root of 3665605561 is about 1541.8729055643.

The spelling of 3665605561 in words is "three billion, six hundred sixty-five million, six hundred five thousand, five hundred sixty-one".