66664891 has 4 divisors (see below), whose sum is σ = 66681832. Its totient is φ = 66647952.

The previous prime is 66664889. The next prime is 66664907. The reversal of 66664891 is 19846666.

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 66664891 - 2¹ = 66664889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66664391) 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, 856 + ... + 11578.

It is an arithmetic number, because the mean of its divisors is an integer number (16670458).

Almost surely, 2^66664891 is an apocalyptic number.

66664891 is a deficient number, since it is larger than the sum of its proper divisors (16941).

66664891 is a wasteful number, since it uses less digits than its factorization.

66664891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16940.

The product of its digits is 373248, while the sum is 46.

The square root of 66664891 is about 8164.8570716210. The cubic root of 66664891 is about 405.4765330185.

The spelling of 66664891 in words is "sixty-six million, six hundred sixty-four thousand, eight hundred ninety-one".