205621813 has 2 divisors, whose sum is σ = 205621814. Its totient is φ = 205621812.

The previous prime is 205621807. The next prime is 205621831. The reversal of 205621813 is 318126502.

Together with next prime (205621831) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 137757169 + 67864644 = 11737^2 + 8238^2 .

It is a cyclic number.

It is not a de Polignac number, because 205621813 - 2²¹ = 203524661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205625813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102810906 + 102810907.

It is an arithmetic number, because the mean of its divisors is an integer number (102810907).

Almost surely, 2^205621813 is an apocalyptic number.

It is an amenable number.

205621813 is a deficient number, since it is larger than the sum of its proper divisors (1).

205621813 is an equidigital number, since it uses as much as digits as its factorization.

205621813 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 205621813 is about 14339.5192736716. The cubic root of 205621813 is about 590.2324211173.

The spelling of 205621813 in words is "two hundred five million, six hundred twenty-one thousand, eight hundred thirteen".