66010221 has 18 divisors (see below), whose sum is σ = 99020142. Its totient is φ = 44002440.

The previous prime is 66010213. The next prime is 66010223. The reversal of 66010221 is 12201066.

It is a happy number.

66010221 is a `hidden beast` number, since 660 + 1 + 0 + 2 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 57972996 + 8037225 = 7614^2 + 2835^2 .

It is not a de Polignac number, because 66010221 - 2³ = 66010213 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 66010194 and 66010203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66010223) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 1531 + ... + 11591.

It is an arithmetic number, because the mean of its divisors is an integer number (5501119).

Almost surely, 2^66010221 is an apocalyptic number.

It is an amenable number.

66010221 is a deficient number, since it is larger than the sum of its proper divisors (33009921).

66010221 is an frugal number, since it uses more digits than its factorization.

66010221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10085 (or 10064 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 66010221 is about 8124.6674393479. The cubic root of 66010221 is about 404.1448623563.

Adding to 66010221 its reverse (12201066), we get a palindrome (78211287).

The spelling of 66010221 in words is "sixty-six million, ten thousand, two hundred twenty-one".