665544643 has 4 divisors (see below), whose sum is σ = 670785280. Its totient is φ = 660304008.

The previous prime is 665544637. The next prime is 665544653. The reversal of 665544643 is 346445566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 346445566 = 2 ⋅173222783.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665544643 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 665544643.

It is not an unprimeable number, because it can be changed into a prime (665544653) 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, 2620128 + ... + 2620381.

It is an arithmetic number, because the mean of its divisors is an integer number (167696320).

Almost surely, 2^665544643 is an apocalyptic number.

665544643 is a deficient number, since it is larger than the sum of its proper divisors (5240637).

665544643 is a wasteful number, since it uses less digits than its factorization.

665544643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5240636.

The product of its digits is 1036800, while the sum is 43.

The square root of 665544643 is about 25798.1519299348. The cubic root of 665544643 is about 873.0901005551.

The spelling of 665544643 in words is "six hundred sixty-five million, five hundred forty-four thousand, six hundred forty-three".