205212121057 has 4 divisors (see below), whose sum is σ = 206063623876. Its totient is φ = 204360618240.

The previous prime is 205212121039. The next prime is 205212121067. The reversal of 205212121057 is 750121212502.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 122273304976 + 82938816081 = 349676^2 + 287991^2 .

It is a cyclic number.

It is not a de Polignac number, because 205212121057 - 2¹⁹ = 205211596769 is a prime.

It is a super-2 number, since 2×205212121057² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205212121007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 425751048 + ... + 425751529.

It is an arithmetic number, because the mean of its divisors is an integer number (51515905969).

Almost surely, 2^205212121057 is an apocalyptic number.

It is an amenable number.

205212121057 is a deficient number, since it is larger than the sum of its proper divisors (851502819).

205212121057 is an equidigital number, since it uses as much as digits as its factorization.

205212121057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 851502818.

The product of its (nonzero) digits is 2800, while the sum is 28.

Adding to 205212121057 its reverse (750121212502), we get a palindrome (955333333559).

The spelling of 205212121057 in words is "two hundred five billion, two hundred twelve million, one hundred twenty-one thousand, fifty-seven".