205240421 has 2 divisors, whose sum is σ = 205240422. Its totient is φ = 205240420.

The previous prime is 205240411. The next prime is 205240423. The reversal of 205240421 is 124042502.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 123988225 + 81252196 = 11135^2 + 9014^2 .

It is a cyclic number.

It is not a de Polignac number, because 205240421 - 2²² = 201046117 is a prime.

Together with 205240423, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 205240393 and 205240402.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205240423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102620210 + 102620211.

It is an arithmetic number, because the mean of its divisors is an integer number (102620211).

Almost surely, 2^205240421 is an apocalyptic number.

It is an amenable number.

205240421 is a deficient number, since it is larger than the sum of its proper divisors (1).

205240421 is an equidigital number, since it uses as much as digits as its factorization.

205240421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 205240421 is about 14326.2144685887. The cubic root of 205240421 is about 589.8672697689.

Adding to 205240421 its reverse (124042502), we get a palindrome (329282923).

The spelling of 205240421 in words is "two hundred five million, two hundred forty thousand, four hundred twenty-one".