66553221 has 24 divisors (see below), whose sum is σ = 104405760. Its totient is φ = 37595712.

The previous prime is 66553217. The next prime is 66553247. The reversal of 66553221 is 12235566.

It is not a de Polignac number, because 66553221 - 2² = 66553217 is a prime.

It is a Curzon number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66553321) 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, 10540 + ... + 15626.

It is an arithmetic number, because the mean of its divisors is an integer number (4350240).

Almost surely, 2^66553221 is an apocalyptic number.

66553221 is the 4361-st nonagonal number.

It is an amenable number.

66553221 is a deficient number, since it is larger than the sum of its proper divisors (37852539).

66553221 is a wasteful number, since it uses less digits than its factorization.

66553221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5193 (or 5186 counting only the distinct ones).

The product of its digits is 10800, while the sum is 30.

The square root of 66553221 is about 8158.0157513945. The cubic root of 66553221 is about 405.2500026323.

Adding to 66553221 its reverse (12235566), we get a palindrome (78788787).

The spelling of 66553221 in words is "sixty-six million, five hundred fifty-three thousand, two hundred twenty-one".