205891017221 has 16 divisors (see below), whose sum is σ = 215139575040. Its totient is φ = 196795085760.

The previous prime is 205891017193. The next prime is 205891017229. The reversal of 205891017221 is 122710198502.

205891017221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a de Polignac number, because none of the positive numbers 2^k-205891017221 is a prime.

It is a super-2 number, since 2×205891017221² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205891017229) 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 15 ways as a sum of consecutive naturals, for example, 1150430 + ... + 1317296.

It is an arithmetic number, because the mean of its divisors is an integer number (13446223440).

Almost surely, 2^205891017221 is an apocalyptic number.

It is an amenable number.

205891017221 is a deficient number, since it is larger than the sum of its proper divisors (9248557819).

205891017221 is a wasteful number, since it uses less digits than its factorization.

205891017221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167324.

The product of its (nonzero) digits is 20160, while the sum is 38.

The spelling of 205891017221 in words is "two hundred five billion, eight hundred ninety-one million, seventeen thousand, two hundred twenty-one".