205122721 has 2 divisors, whose sum is σ = 205122722. Its totient is φ = 205122720.

The previous prime is 205122719. The next prime is 205122739. The reversal of 205122721 is 127221502.

205122721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 168350625 + 36772096 = 12975^2 + 6064^2 .

It is a cyclic number.

It is not a de Polignac number, because 205122721 - 2¹ = 205122719 is a prime.

Together with 205122719, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 205122692 and 205122701.

It is not a weakly prime, because it can be changed into another prime (205125721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102561360 + 102561361.

It is an arithmetic number, because the mean of its divisors is an integer number (102561361).

Almost surely, 2^205122721 is an apocalyptic number.

It is an amenable number.

205122721 is a deficient number, since it is larger than the sum of its proper divisors (1).

205122721 is an equidigital number, since it uses as much as digits as its factorization.

205122721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 205122721 is about 14322.1060253023. The cubic root of 205122721 is about 589.7544904033.

The spelling of 205122721 in words is "two hundred five million, one hundred twenty-two thousand, seven hundred twenty-one".