206256721 has 6 divisors (see below), whose sum is σ = 226712066. Its totient is φ = 187506000.

The previous prime is 206256719. The next prime is 206256737. The reversal of 206256721 is 127652602.

It can be written as a sum of positive squares in only one way, i.e., 159744321 + 46512400 = 12639^2 + 6820^2 .

It is not a de Polignac number, because 206256721 - 2¹ = 206256719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (206256781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 852180 + ... + 852421.

Almost surely, 2^206256721 is an apocalyptic number.

It is an amenable number.

206256721 is a deficient number, since it is larger than the sum of its proper divisors (20455345).

206256721 is a wasteful number, since it uses less digits than its factorization.

206256721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1704623 (or 1704612 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 206256721 is about 14361.6406096240. The cubic root of 206256721 is about 590.8392929220.

The spelling of 206256721 in words is "two hundred six million, two hundred fifty-six thousand, seven hundred twenty-one".