66609985891 has 2 divisors, whose sum is σ = 66609985892. Its totient is φ = 66609985890.

The previous prime is 66609985829. The next prime is 66609985969. The reversal of 66609985891 is 19858990666.

66609985891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 66609985891 - 2¹³ = 66609977699 is a prime.

It is not a weakly prime, because it can be changed into another prime (66609985591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33304992945 + 33304992946.

It is an arithmetic number, because the mean of its divisors is an integer number (33304992946).

Almost surely, 2^66609985891 is an apocalyptic number.

66609985891 is a deficient number, since it is larger than the sum of its proper divisors (1).

66609985891 is an equidigital number, since it uses as much as digits as its factorization.

66609985891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 50388480, while the sum is 67.

The spelling of 66609985891 in words is "sixty-six billion, six hundred nine million, nine hundred eighty-five thousand, eight hundred ninety-one".