66239968921 has 16 divisors (see below), whose sum is σ = 78707077120. Its totient is φ = 54550279440.

The previous prime is 66239968891. The next prime is 66239968943. The reversal of 66239968921 is 12986993266.

It is a cyclic number.

It is not a de Polignac number, because 66239968921 - 2⁹ = 66239968409 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66239968921.

It is not an unprimeable number, because it can be changed into a prime (66239968321) 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, 1067871 + ... + 1128196.

It is an arithmetic number, because the mean of its divisors is an integer number (4919192320).

Almost surely, 2^66239968921 is an apocalyptic number.

It is an amenable number.

66239968921 is a deficient number, since it is larger than the sum of its proper divisors (12467108199).

66239968921 is a wasteful number, since it uses less digits than its factorization.

66239968921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2196244.

The product of its digits is 15116544, while the sum is 61.

The spelling of 66239968921 in words is "sixty-six billion, two hundred thirty-nine million, nine hundred sixty-eight thousand, nine hundred twenty-one".