217728345221 has 8 divisors (see below), whose sum is σ = 219189178944. Its totient is φ = 216267760800.

The previous prime is 217728345209. The next prime is 217728345259. The reversal of 217728345221 is 122543827712.

It is a happy number.

217728345221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217728345221 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 (217728345271) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1895585 + ... + 2007161.

It is an arithmetic number, because the mean of its divisors is an integer number (27398647368).

Almost surely, 2^217728345221 is an apocalyptic number.

It is an amenable number.

217728345221 is a deficient number, since it is larger than the sum of its proper divisors (1460833723).

217728345221 is a wasteful number, since it uses less digits than its factorization.

217728345221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124651.

The product of its digits is 376320, while the sum is 44.

The spelling of 217728345221 in words is "two hundred seventeen billion, seven hundred twenty-eight million, three hundred forty-five thousand, two hundred twenty-one".