66213753921 has 24 divisors (see below), whose sum is σ = 109314121280. Its totient is φ = 37833358176.

The previous prime is 66213753919. The next prime is 66213753973. The reversal of 66213753921 is 12935731266.

66213753921 is a `hidden beast` number, since 6 + 62 + 1 + 37 + 539 + 21 = 666.

66213753921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 66213753921 - 2¹ = 66213753919 is a prime.

It is a super-2 number, since 2×66213753921² (a number of 22 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (66213753901) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 904935 + ... + 975363.

Almost surely, 2^66213753921 is an apocalyptic number.

It is an amenable number.

66213753921 is a deficient number, since it is larger than the sum of its proper divisors (43100367359).

66213753921 is a wasteful number, since it uses less digits than its factorization.

66213753921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85365 (or 85362 counting only the distinct ones).

The product of its digits is 408240, while the sum is 45.

The spelling of 66213753921 in words is "sixty-six billion, two hundred thirteen million, seven hundred fifty-three thousand, nine hundred twenty-one".