661659805 has 8 divisors (see below), whose sum is σ = 840697272. Its totient is φ = 498190848.

The previous prime is 661659769. The next prime is 661659811. The reversal of 661659805 is 508956166.

It can be written as a sum of positive squares in 4 ways, for example, as 279926361 + 381733444 = 16731^2 + 19538^2 .

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

It is not a de Polignac number, because 661659805 - 2⁹ = 661659293 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3892032 + ... + 3892201.

It is an arithmetic number, because the mean of its divisors is an integer number (105087159).

Almost surely, 2^661659805 is an apocalyptic number.

It is an amenable number.

661659805 is a deficient number, since it is larger than the sum of its proper divisors (179037467).

661659805 is a wasteful number, since it uses less digits than its factorization.

661659805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7784255.

The product of its (nonzero) digits is 388800, while the sum is 46.

The square root of 661659805 is about 25722.7487839072. The cubic root of 661659805 is about 871.3880186335.

The spelling of 661659805 in words is "six hundred sixty-one million, six hundred fifty-nine thousand, eight hundred five".