66904358539221 has 18 divisors (see below), whose sum is σ = 112417527614262. Its totient is φ = 38231062022160.

The previous prime is 66904358539211. The next prime is 66904358539223. The reversal of 66904358539221 is 12293585340966.

It is a happy number.

66904358539221 is a `hidden beast` number, since 6 + 6 + 9 + 0 + 4 + 358 + 53 + 9 + 221 = 666.

It can be written as a sum of positive squares in only one way, i.e., 64577070992196 + 2327287547025 = 8035986^2 + 1525545^2 .

It is not a de Polignac number, because 66904358539221 - 2⁷ = 66904358539093 is a prime.

It is a Smith number, since the sum of its digits (63) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66904358539223) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 75855281350 + ... + 75855282231.

Almost surely, 2^{66904358539221} is an apocalyptic number.

It is an amenable number.

66904358539221 is a deficient number, since it is larger than the sum of its proper divisors (45513169075041).

66904358539221 is a wasteful number, since it uses less digits than its factorization.

66904358539221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151710563601 (or 151710563591 counting only the distinct ones).

The product of its (nonzero) digits is 83980800, while the sum is 63.

The spelling of 66904358539221 in words is "sixty-six trillion, nine hundred four billion, three hundred fifty-eight million, five hundred thirty-nine thousand, two hundred twenty-one".