205223017021 has 4 divisors (see below), whose sum is σ = 223879654944. Its totient is φ = 186566379100.

The previous prime is 205223016979. The next prime is 205223017031. The reversal of 205223017021 is 120710322502.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205223017021 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205223017031) 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, 9328318945 + ... + 9328318966.

It is an arithmetic number, because the mean of its divisors is an integer number (55969913736).

Almost surely, 2^205223017021 is an apocalyptic number.

It is an amenable number.

205223017021 is a deficient number, since it is larger than the sum of its proper divisors (18656637923).

205223017021 is a wasteful number, since it uses less digits than its factorization.

205223017021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18656637922.

The product of its (nonzero) digits is 1680, while the sum is 25.

Adding to 205223017021 its reverse (120710322502), we get a palindrome (325933339523).

The spelling of 205223017021 in words is "two hundred five billion, two hundred twenty-three million, seventeen thousand, twenty-one".