205820721 has 12 divisors (see below), whose sum is σ = 310222848. Its totient is φ = 131247864.

The previous prime is 205820707. The next prime is 205820723. The reversal of 205820721 is 127028502.

It is not a de Polignac number, because 205820721 - 2⁵ = 205820689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (205820723) 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 in 11 ways as a sum of consecutive naturals, for example, 496945 + ... + 497358.

It is an arithmetic number, because the mean of its divisors is an integer number (25851904).

Almost surely, 2^205820721 is an apocalyptic number.

It is an amenable number.

205820721 is a deficient number, since it is larger than the sum of its proper divisors (104402127).

205820721 is a wasteful number, since it uses less digits than its factorization.

205820721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 994332 (or 994329 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 205820721 is about 14346.4532550732. The cubic root of 205820721 is about 590.4226799762.

The spelling of 205820721 in words is "two hundred five million, eight hundred twenty thousand, seven hundred twenty-one".