66505650891 has 16 divisors (see below), whose sum is σ = 89607536928. Its totient is φ = 43870976000.

The previous prime is 66505650881. The next prime is 66505650941. The reversal of 66505650891 is 19805650566.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 66505650891 - 2²³ = 66497262283 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66505650881) 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, 428971 + ... + 563051.

It is an arithmetic number, because the mean of its divisors is an integer number (5600471058).

Almost surely, 2^66505650891 is an apocalyptic number.

66505650891 is a deficient number, since it is larger than the sum of its proper divisors (23101886037).

66505650891 is a wasteful number, since it uses less digits than its factorization.

66505650891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135822.

The product of its (nonzero) digits is 1944000, while the sum is 51.

The spelling of 66505650891 in words is "sixty-six billion, five hundred five million, six hundred fifty thousand, eight hundred ninety-one".