66505221 has 6 divisors (see below), whose sum is σ = 96063110. Its totient is φ = 44336808.

The previous prime is 66505217. The next prime is 66505249. The reversal of 66505221 is 12250566.

66505221 is a `hidden beast` number, since 6 + 650 + 5 + 2 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 66096900 + 408321 = 8130^2 + 639^2 .

It is not a de Polignac number, because 66505221 - 2² = 66505217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66505421) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3694726 + ... + 3694743.

Almost surely, 2^66505221 is an apocalyptic number.

It is an amenable number.

66505221 is a deficient number, since it is larger than the sum of its proper divisors (29557889).

66505221 is a wasteful number, since it uses less digits than its factorization.

66505221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7389475 (or 7389472 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 66505221 is about 8155.0733289162. The cubic root of 66505221 is about 405.1525534122.

Adding to 66505221 its reverse (12250566), we get a palindrome (78755787).

The spelling of 66505221 in words is "sixty-six million, five hundred five thousand, two hundred twenty-one".