66638321172 has 18 divisors (see below), whose sum is σ = 168446867498. Its totient is φ = 22212773712.

The previous prime is 66638321149. The next prime is 66638321179. The reversal of 66638321172 is 27112383666.

It can be written as a sum of positive squares in only one way, i.e., 65227116816 + 1411204356 = 255396^2 + 37566^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66638321179) 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 5 ways as a sum of consecutive naturals, for example, 925532203 + ... + 925532274.

Almost surely, 2^66638321172 is an apocalyptic number.

It is an amenable number.

66638321172 is an abundant number, since it is smaller than the sum of its proper divisors (101808546326).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66638321172 is a wasteful number, since it uses less digits than its factorization.

66638321172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1851064487 (or 1851064482 counting only the distinct ones).

The product of its digits is 435456, while the sum is 45.

The spelling of 66638321172 in words is "sixty-six billion, six hundred thirty-eight million, three hundred twenty-one thousand, one hundred seventy-two".