205256721 has 4 divisors (see below), whose sum is σ = 273675632. Its totient is φ = 136837812.

The previous prime is 205256699. The next prime is 205256729. The reversal of 205256721 is 127652502.

205256721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 205256721 - 2¹⁸ = 204994577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205256729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34209451 + ... + 34209456.

It is an arithmetic number, because the mean of its divisors is an integer number (68418908).

Almost surely, 2^205256721 is an apocalyptic number.

It is an amenable number.

205256721 is a deficient number, since it is larger than the sum of its proper divisors (68418911).

205256721 is an equidigital number, since it uses as much as digits as its factorization.

205256721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68418910.

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 205256721 is about 14326.7833444915. The cubic root of 205256721 is about 589.8828849223.

The spelling of 205256721 in words is "two hundred five million, two hundred fifty-six thousand, seven hundred twenty-one".