66305221 has 4 divisors (see below), whose sum is σ = 68097292. Its totient is φ = 64513152.

The previous prime is 66305209. The next prime is 66305237. The reversal of 66305221 is 12250366.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12250366 = 2 ⋅6125183.

It can be written as a sum of positive squares in 2 ways, for example, as 42393121 + 23912100 = 6511^2 + 4890^2 .

It is a cyclic number.

It is not a de Polignac number, because 66305221 - 2¹³ = 66297029 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 (66305521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 895980 + ... + 896053.

It is an arithmetic number, because the mean of its divisors is an integer number (17024323).

Almost surely, 2^66305221 is an apocalyptic number.

It is an amenable number.

66305221 is a deficient number, since it is larger than the sum of its proper divisors (1792071).

66305221 is a wasteful number, since it uses less digits than its factorization.

66305221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1792070.

The product of its (nonzero) digits is 2160, while the sum is 25.

The square root of 66305221 is about 8142.8017905387. The cubic root of 66305221 is about 404.7460095216.

Adding to 66305221 its reverse (12250366), we get a palindrome (78555587).

The spelling of 66305221 in words is "sixty-six million, three hundred five thousand, two hundred twenty-one".