205157566821 has 4 divisors (see below), whose sum is σ = 273543422432. Its totient is φ = 136771711212.

The previous prime is 205157566769. The next prime is 205157566829. The reversal of 205157566821 is 128665751502.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 205157566821 - 2¹⁰ = 205157565797 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 (205157566829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34192927801 + ... + 34192927806.

It is an arithmetic number, because the mean of its divisors is an integer number (68385855608).

Almost surely, 2^205157566821 is an apocalyptic number.

It is an amenable number.

205157566821 is a deficient number, since it is larger than the sum of its proper divisors (68385855611).

205157566821 is an equidigital number, since it uses as much as digits as its factorization.

205157566821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68385855610.

The product of its (nonzero) digits is 1008000, while the sum is 48.

The spelling of 205157566821 in words is "two hundred five billion, one hundred fifty-seven million, five hundred sixty-six thousand, eight hundred twenty-one".