66221867861 has 4 divisors (see below), whose sum is σ = 66434800224. Its totient is φ = 66008935500.

The previous prime is 66221867857. The next prime is 66221867863. The reversal of 66221867861 is 16876812266.

It is a happy number.

66221867861 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16876812266 = 2 ⋅8438406133.

It is a cyclic number.

It is not a de Polignac number, because 66221867861 - 2² = 66221867857 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66221867863) 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, 106465715 + ... + 106466336.

It is an arithmetic number, because the mean of its divisors is an integer number (16608700056).

Almost surely, 2^66221867861 is an apocalyptic number.

It is an amenable number.

66221867861 is a deficient number, since it is larger than the sum of its proper divisors (212932363).

66221867861 is a wasteful number, since it uses less digits than its factorization.

66221867861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212932362.

The product of its digits is 2322432, while the sum is 53.

The spelling of 66221867861 in words is "sixty-six billion, two hundred twenty-one million, eight hundred sixty-seven thousand, eight hundred sixty-one".