66766821 has 32 divisors (see below), whose sum is σ = 99532800. Its totient is φ = 39473280.

The previous prime is 66766807. The next prime is 66766853. The reversal of 66766821 is 12866766.

It is a happy number.

It is not a de Polignac number, because 66766821 - 2¹¹ = 66764773 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66766891) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 372910 + ... + 373088.

It is an arithmetic number, because the mean of its divisors is an integer number (3110400).

Almost surely, 2^66766821 is an apocalyptic number.

It is an amenable number.

66766821 is a deficient number, since it is larger than the sum of its proper divisors (32765979).

66766821 is a wasteful number, since it uses less digits than its factorization.

66766821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 409.

The product of its digits is 145152, while the sum is 42.

The square root of 66766821 is about 8171.0966828205. The cubic root of 66766821 is about 405.6830844019.

The spelling of 66766821 in words is "sixty-six million, seven hundred sixty-six thousand, eight hundred twenty-one".