205601821 has 2 divisors, whose sum is σ = 205601822. Its totient is φ = 205601820.

The previous prime is 205601819. The next prime is 205601849. The reversal of 205601821 is 128106502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 198387225 + 7214596 = 14085^2 + 2686^2 .

It is a cyclic number.

It is not a de Polignac number, because 205601821 - 2¹ = 205601819 is a prime.

Together with 205601819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205601801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102800910 + 102800911.

It is an arithmetic number, because the mean of its divisors is an integer number (102800911).

Almost surely, 2^205601821 is an apocalyptic number.

It is an amenable number.

205601821 is a deficient number, since it is larger than the sum of its proper divisors (1).

205601821 is an equidigital number, since it uses as much as digits as its factorization.

205601821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 205601821 is about 14338.8221622280. The cubic root of 205601821 is about 590.2132916471.

The spelling of 205601821 in words is "two hundred five million, six hundred one thousand, eight hundred twenty-one".