1665885661 has 16 divisors (see below), whose sum is σ = 1890111168. Its totient is φ = 1454947200.

The previous prime is 1665885659. The next prime is 1665885701.

1665885661 is nontrivially palindromic in base 10.

It is a cyclic number.

It is not a de Polignac number, because 1665885661 - 2¹ = 1665885659 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1665885599 and 1665885608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665888661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16 + ... + 57721.

It is an arithmetic number, because the mean of its divisors is an integer number (118131948).

Almost surely, 2^1665885661 is an apocalyptic number.

1665885661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1665885661 is a deficient number, since it is larger than the sum of its proper divisors (224225507).

1665885661 is a wasteful number, since it uses less digits than its factorization.

1665885661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57852.

The product of its digits is 2073600, while the sum is 52.

The square root of 1665885661 is about 40815.2625986897. The cubic root of 1665885661 is about 1185.4458756394.

The spelling of 1665885661 in words is "one billion, six hundred sixty-five million, eight hundred eighty-five thousand, six hundred sixty-one".