206385721 has 4 divisors (see below), whose sum is σ = 213502500. Its totient is φ = 199268944.

The previous prime is 206385709. The next prime is 206385727. The reversal of 206385721 is 127583602.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 127583602 = 2 ⋅63791801.

It can be written as a sum of positive squares in 2 ways, for example, as 159668496 + 46717225 = 12636^2 + 6835^2 .

It is a cyclic number.

It is not a de Polignac number, because 206385721 - 2⁵ = 206385689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (206385727) 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 3 ways as a sum of consecutive naturals, for example, 3558346 + ... + 3558403.

It is an arithmetic number, because the mean of its divisors is an integer number (53375625).

Almost surely, 2^206385721 is an apocalyptic number.

It is an amenable number.

206385721 is a deficient number, since it is larger than the sum of its proper divisors (7116779).

206385721 is an equidigital number, since it uses as much as digits as its factorization.

206385721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7116778.

The product of its (nonzero) digits is 20160, while the sum is 34.

The square root of 206385721 is about 14366.1310379656. The cubic root of 206385721 is about 590.9624442778.

The spelling of 206385721 in words is "two hundred six million, three hundred eighty-five thousand, seven hundred twenty-one".