666620443561 has 8 divisors (see below), whose sum is σ = 670779635904. Its totient is φ = 662463245040.

The previous prime is 666620443549. The next prime is 666620443609. The reversal of 666620443561 is 165344026666.

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 666620443561 - 2⁵ = 666620443529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666620443061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175146 + ... + 1167868.

It is an arithmetic number, because the mean of its divisors is an integer number (83847454488).

Almost surely, 2^666620443561 is an apocalyptic number.

It is an amenable number.

666620443561 is a deficient number, since it is larger than the sum of its proper divisors (4159192343).

666620443561 is a wasteful number, since it uses less digits than its factorization.

666620443561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 996911.

The product of its (nonzero) digits is 3732480, while the sum is 49.

The spelling of 666620443561 in words is "six hundred sixty-six billion, six hundred twenty million, four hundred forty-three thousand, five hundred sixty-one".