66656921 has 8 divisors (see below), whose sum is σ = 73216320. Its totient is φ = 60402672.

The previous prime is 66656911. The next prime is 66656927. The reversal of 66656921 is 12965666.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66656921 - 2¹⁴ = 66640537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66656927) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 75830 + ... + 76703.

It is an arithmetic number, because the mean of its divisors is an integer number (9152040).

Almost surely, 2^66656921 is an apocalyptic number.

It is an amenable number.

66656921 is a deficient number, since it is larger than the sum of its proper divisors (6559399).

66656921 is a wasteful number, since it uses less digits than its factorization.

66656921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152575.

The product of its digits is 116640, while the sum is 41.

The square root of 66656921 is about 8164.3689897015. The cubic root of 66656921 is about 405.4603737043.

The spelling of 66656921 in words is "sixty-six million, six hundred fifty-six thousand, nine hundred twenty-one".