665891993 has 16 divisors (see below), whose sum is σ = 759124800. Its totient is φ = 579026880.

The previous prime is 665891987. The next prime is 665892041. The reversal of 665891993 is 399198566.

665891993 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665891993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665891293) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36683 + ... + 51743.

It is an arithmetic number, because the mean of its divisors is an integer number (47445300).

Almost surely, 2^665891993 is an apocalyptic number.

It is an amenable number.

665891993 is a deficient number, since it is larger than the sum of its proper divisors (93232807).

665891993 is a wasteful number, since it uses less digits than its factorization.

665891993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15272.

The product of its digits is 3149280, while the sum is 56.

The square root of 665891993 is about 25804.8831231610. The cubic root of 665891993 is about 873.2419636976.

The spelling of 665891993 in words is "six hundred sixty-five million, eight hundred ninety-one thousand, nine hundred ninety-three".