205120321 has 6 divisors (see below), whose sum is σ = 238609410. Its totient is φ = 175817376.

The previous prime is 205120319. The next prime is 205120339. The reversal of 205120321 is 123021502.

It can be written as a sum of positive squares in only one way, i.e., 106316721 + 98803600 = 10311^2 + 9940^2 .

It is not a de Polignac number, because 205120321 - 2¹ = 205120319 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 205120295 and 205120304.

It is not an unprimeable number, because it can be changed into a prime (205120021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2093016 + ... + 2093113.

It is an arithmetic number, because the mean of its divisors is an integer number (39768235).

Almost surely, 2^205120321 is an apocalyptic number.

It is an amenable number.

205120321 is a deficient number, since it is larger than the sum of its proper divisors (33489089).

205120321 is an equidigital number, since it uses as much as digits as its factorization.

205120321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4186143 (or 4186136 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 205120321 is about 14322.0222384969. The cubic root of 205120321 is about 589.7521902903.

Adding to 205120321 its reverse (123021502), we get a palindrome (328141823).

The spelling of 205120321 in words is "two hundred five million, one hundred twenty thousand, three hundred twenty-one".