66921647858 has 18 divisors (see below), whose sum is σ = 108705905037. Its totient is φ = 30884719320.

The previous prime is 66921647851. The next prime is 66921647879. The reversal of 66921647858 is 85874612966.

It can be written as a sum of positive squares in 2 ways, for example, as 57219988849 + 9701659009 = 239207^2 + 98497^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=182923.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66921647858.

It is not an unprimeable number, because it can be changed into a prime (66921647851) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 4748963 + ... + 4763033.

Almost surely, 2^66921647858 is an apocalyptic number.

66921647858 is a deficient number, since it is larger than the sum of its proper divisors (41784257179).

66921647858 is an frugal number, since it uses more digits than its factorization.

66921647858 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28170 (or 14086 counting only the distinct ones).

The product of its digits is 34836480, while the sum is 62.

The spelling of 66921647858 in words is "sixty-six billion, nine hundred twenty-one million, six hundred forty-seven thousand, eight hundred fifty-eight".