66606623721 has 24 divisors (see below), whose sum is σ = 104974889760. Its totient is φ = 40360344000.

The previous prime is 66606623693. The next prime is 66606623737. The reversal of 66606623721 is 12732660666.

It is not a de Polignac number, because 66606623721 - 2¹⁴ = 66606607337 is a prime.

It is a super-3 number, since 3×66606623721³ (a number of 33 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (66606623761) 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 23 ways as a sum of consecutive naturals, for example, 516310 + ... + 632288.

It is an arithmetic number, because the mean of its divisors is an integer number (4373953740).

Almost surely, 2^66606623721 is an apocalyptic number.

It is an amenable number.

66606623721 is a deficient number, since it is larger than the sum of its proper divisors (38368266039).

66606623721 is a wasteful number, since it uses less digits than its factorization.

66606623721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121797 (or 121794 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 45.

The spelling of 66606623721 in words is "sixty-six billion, six hundred six million, six hundred twenty-three thousand, seven hundred twenty-one".