66721838775 has 24 divisors (see below), whose sum is σ = 116119413120. Its totient is φ = 33712086240.

The previous prime is 66721838747. The next prime is 66721838783. The reversal of 66721838775 is 57783812766.

It is a happy number.

It is not a de Polignac number, because 66721838775 - 2⁹ = 66721838263 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 23409747 + ... + 23412596.

It is an arithmetic number, because the mean of its divisors is an integer number (4838308880).

Almost surely, 2^66721838775 is an apocalyptic number.

66721838775 is a deficient number, since it is larger than the sum of its proper divisors (49397574345).

66721838775 is a wasteful number, since it uses less digits than its factorization.

66721838775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46822375 (or 46822370 counting only the distinct ones).

The product of its digits is 23708160, while the sum is 60.

The spelling of 66721838775 in words is "sixty-six billion, seven hundred twenty-one million, eight hundred thirty-eight thousand, seven hundred seventy-five".