66840906091 has 4 divisors (see below), whose sum is σ = 68997064384. Its totient is φ = 64684747800.

The previous prime is 66840906061. The next prime is 66840906103. The reversal of 66840906091 is 19060904866.

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 66840906091 - 2²⁵ = 66807351659 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66840906031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1078079100 + ... + 1078079161.

It is an arithmetic number, because the mean of its divisors is an integer number (17249266096).

Almost surely, 2^66840906091 is an apocalyptic number.

66840906091 is a deficient number, since it is larger than the sum of its proper divisors (2156158293).

66840906091 is a wasteful number, since it uses less digits than its factorization.

66840906091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2156158292.

The product of its (nonzero) digits is 559872, while the sum is 49.

The spelling of 66840906091 in words is "sixty-six billion, eight hundred forty million, nine hundred six thousand, ninety-one".