205121005 has 4 divisors (see below), whose sum is σ = 246145212. Its totient is φ = 164096800.

The previous prime is 205121003. The next prime is 205121009. The reversal of 205121005 is 500121502.

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 39175081 + 165945924 = 6259^2 + 12882^2 .

It is not a de Polignac number, because 205121005 - 2¹ = 205121003 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 205121005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205121003) 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, 20512096 + ... + 20512105.

It is an arithmetic number, because the mean of its divisors is an integer number (61536303).

Almost surely, 2^205121005 is an apocalyptic number.

It is an amenable number.

205121005 is a deficient number, since it is larger than the sum of its proper divisors (41024207).

205121005 is an equidigital number, since it uses as much as digits as its factorization.

205121005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41024206.

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 205121005 is about 14322.0461177864. The cubic root of 205121005 is about 589.7528458243.

Adding to 205121005 its reverse (500121502), we get a palindrome (705242507).

The spelling of 205121005 in words is "two hundred five million, one hundred twenty-one thousand, five".