665561643 has 8 divisors (see below), whose sum is σ = 893293056. Its totient is φ = 440769000.

The previous prime is 665561641. The next prime is 665561653. The reversal of 665561643 is 346165566.

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

It is not a de Polignac number, because 665561643 - 2¹ = 665561641 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 665561595 and 665561604.

It is not an unprimeable number, because it can be changed into a prime (665561641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 734163 + ... + 735068.

It is an arithmetic number, because the mean of its divisors is an integer number (111661632).

Almost surely, 2^665561643 is an apocalyptic number.

665561643 is a deficient number, since it is larger than the sum of its proper divisors (227731413).

665561643 is a wasteful number, since it uses less digits than its factorization.

665561643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1469385.

The product of its digits is 388800, while the sum is 42.

The square root of 665561643 is about 25798.4814087961. The cubic root of 665561643 is about 873.0975342690.

The spelling of 665561643 in words is "six hundred sixty-five million, five hundred sixty-one thousand, six hundred forty-three".