205543251521 has 8 divisors (see below), whose sum is σ = 211580415144. Its totient is φ = 199586050560.

The previous prime is 205543251491. The next prime is 205543251643. The reversal of 205543251521 is 125152345502.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 8748983296 + 196794268225 = 93536^2 + 443615^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 205543251521 - 2³⁰ = 204469509697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205543251421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19985450 + ... + 19995731.

It is an arithmetic number, because the mean of its divisors is an integer number (26447551893).

Almost surely, 2^205543251521 is an apocalyptic number.

It is an amenable number.

205543251521 is a deficient number, since it is larger than the sum of its proper divisors (6037163623).

205543251521 is an equidigital number, since it uses as much as digits as its factorization.

205543251521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39981331.

The product of its (nonzero) digits is 60000, while the sum is 35.

The spelling of 205543251521 in words is "two hundred five billion, five hundred forty-three million, two hundred fifty-one thousand, five hundred twenty-one".