217657120221 has 20 divisors (see below), whose sum is σ = 344268126972. Its totient is φ = 136569172608.

The previous prime is 217657120211. The next prime is 217657120249. The reversal of 217657120221 is 122021756712.

217657120221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 108231788196 + 109425332025 = 328986^2 + 330795^2 .

It is not a de Polignac number, because 217657120221 - 2²⁹ = 217120249309 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217657120211) 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 19 ways as a sum of consecutive naturals, for example, 79031710 + ... + 79034463.

Almost surely, 2^217657120221 is an apocalyptic number.

It is an amenable number.

217657120221 is a deficient number, since it is larger than the sum of its proper divisors (126611006751).

217657120221 is a wasteful number, since it uses less digits than its factorization.

217657120221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158066202 (or 158066193 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

Adding to 217657120221 its reverse (122021756712), we get a palindrome (339678876933).

The spelling of 217657120221 in words is "two hundred seventeen billion, six hundred fifty-seven million, one hundred twenty thousand, two hundred twenty-one".