66643999 has 4 divisors (see below), whose sum is σ = 66762936. Its totient is φ = 66525064.

The previous prime is 66643933. The next prime is 66644033. The reversal of 66643999 is 99934666.

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 66643999 - 2⁹ = 66643487 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66643909) 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, 58624 + ... + 59749.

It is an arithmetic number, because the mean of its divisors is an integer number (16690734).

Almost surely, 2^66643999 is an apocalyptic number.

66643999 is a deficient number, since it is larger than the sum of its proper divisors (118937).

66643999 is a wasteful number, since it uses less digits than its factorization.

66643999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118936.

The product of its digits is 1889568, while the sum is 52.

The square root of 66643999 is about 8163.5775858382. The cubic root of 66643999 is about 405.4341713861.

The spelling of 66643999 in words is "sixty-six million, six hundred forty-three thousand, nine hundred ninety-nine".