205021021 has 2 divisors, whose sum is σ = 205021022. Its totient is φ = 205021020.

The previous prime is 205021007. The next prime is 205021081. The reversal of 205021021 is 120120502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 204089796 + 931225 = 14286^2 + 965^2 .

It is a cyclic number.

It is not a de Polignac number, because 205021021 - 2¹¹ = 205018973 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 205020992 and 205021010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205021081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102510510 + 102510511.

It is an arithmetic number, because the mean of its divisors is an integer number (102510511).

Almost surely, 2^205021021 is an apocalyptic number.

It is an amenable number.

205021021 is a deficient number, since it is larger than the sum of its proper divisors (1).

205021021 is an equidigital number, since it uses as much as digits as its factorization.

205021021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 205021021 is about 14318.5551296211. Note that the first 3 decimals coincide. The cubic root of 205021021 is about 589.6570073835.

Adding to 205021021 its reverse (120120502), we get a palindrome (325141523).

The spelling of 205021021 in words is "two hundred five million, twenty-one thousand, twenty-one".