6660561661 has 8 divisors (see below), whose sum is σ = 7177173080. Its totient is φ = 6144558912.

The previous prime is 6660561647. The next prime is 6660561671. The reversal of 6660561661 is 1661650666.

It can be written as a sum of positive squares in 4 ways, for example, as 78322500 + 6582239161 = 8850^2 + 81131^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 6660561661 - 2⁵ = 6660561629 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 (6660561601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 129306 + ... + 173323.

It is an arithmetic number, because the mean of its divisors is an integer number (897146635).

Almost surely, 2^6660561661 is an apocalyptic number.

It is an amenable number.

6660561661 is a deficient number, since it is larger than the sum of its proper divisors (516611419).

6660561661 is a wasteful number, since it uses less digits than its factorization.

6660561661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304335.

The product of its (nonzero) digits is 233280, while the sum is 43.

The square root of 6660561661 is about 81612.2641580296. The cubic root of 6660561661 is about 1881.4973792767.

The spelling of 6660561661 in words is "six billion, six hundred sixty million, five hundred sixty-one thousand, six hundred sixty-one".