205853671521 has 9 divisors (see below), whose sum is σ = 297346158291. Its totient is φ = 137234873592.

The previous prime is 205853671501. The next prime is 205853671531. The reversal of 205853671521 is 125176358502.

The square root of 205853671521 is 453711.

It is a perfect power (a square), and thus also a powerful number.

205853671521 is a `hidden beast` number, since 2 + 0 + 5 + 8 + 53 + 6 + 71 + 521 = 666.

It can be written as a sum of positive squares in only one way, i.e., 88914294225 + 116939377296 = 298185^2 + 341964^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 205853671521 - 2¹³ = 205853663329 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (205853671501) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1285515 + ... + 1436751.

Almost surely, 2^205853671521 is an apocalyptic number.

205853671521 is the 453711-st square number.

205853671521 is the 226856-th centered octagonal number.

It is an amenable number.

205853671521 is a deficient number, since it is larger than the sum of its proper divisors (91492486770).

205853671521 is an frugal number, since it uses more digits than its factorization.

205853671521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 302480 (or 151240 counting only the distinct ones).

The product of its (nonzero) digits is 504000, while the sum is 45.

The spelling of 205853671521 in words is "two hundred five billion, eight hundred fifty-three million, six hundred seventy-one thousand, five hundred twenty-one".