66655221 has 4 divisors (see below), whose sum is σ = 88873632. Its totient is φ = 44436812.

The previous prime is 66655213. The next prime is 66655243. The reversal of 66655221 is 12255666.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66655221 - 2³ = 66655213 is a prime.

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 (66655201) 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, 11109201 + ... + 11109206.

It is an arithmetic number, because the mean of its divisors is an integer number (22218408).

Almost surely, 2^66655221 is an apocalyptic number.

It is an amenable number.

66655221 is a deficient number, since it is larger than the sum of its proper divisors (22218411).

66655221 is a wasteful number, since it uses less digits than its factorization.

66655221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22218410.

The product of its digits is 21600, while the sum is 33.

The square root of 66655221 is about 8164.2648781136. The cubic root of 66655221 is about 405.4569267579.

The spelling of 66655221 in words is "sixty-six million, six hundred fifty-five thousand, two hundred twenty-one".