665939643 has 4 divisors (see below), whose sum is σ = 887919528. Its totient is φ = 443959760.

The previous prime is 665939639. The next prime is 665939689. The reversal of 665939643 is 346939566.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 665939643 - 2² = 665939639 is a prime.

It is not an unprimeable number, because it can be changed into a prime (665939633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110989938 + ... + 110989943.

It is an arithmetic number, because the mean of its divisors is an integer number (221979882).

Almost surely, 2^665939643 is an apocalyptic number.

665939643 is a deficient number, since it is larger than the sum of its proper divisors (221979885).

665939643 is a wasteful number, since it uses less digits than its factorization.

665939643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221979884.

The product of its digits is 3149280, while the sum is 51.

The square root of 665939643 is about 25805.8063815103. The cubic root of 665939643 is about 873.2627923943.

The spelling of 665939643 in words is "six hundred sixty-five million, nine hundred thirty-nine thousand, six hundred forty-three".