1666195661 has 4 divisors (see below), whose sum is σ = 1794364572. Its totient is φ = 1538026752.

The previous prime is 1666195649. The next prime is 1666195673. The reversal of 1666195661 is 1665916661.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (1666195649) and next prime (1666195673).

It can be written as a sum of positive squares in 2 ways, for example, as 244453225 + 1421742436 = 15635^2 + 37706^2 .

It is a cyclic number.

It is not a de Polignac number, because 1666195661 - 2¹⁰ = 1666194637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666195621) 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, 64084436 + ... + 64084461.

It is an arithmetic number, because the mean of its divisors is an integer number (448591143).

Almost surely, 2^1666195661 is an apocalyptic number.

It is an amenable number.

1666195661 is a deficient number, since it is larger than the sum of its proper divisors (128168911).

1666195661 is a wasteful number, since it uses less digits than its factorization.

1666195661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128168910.

The product of its digits is 349920, while the sum is 47.

The square root of 1666195661 is about 40819.0600210245. The cubic root of 1666195661 is about 1185.5194031804.

The spelling of 1666195661 in words is "one billion, six hundred sixty-six million, one hundred ninety-five thousand, six hundred sixty-one".