206216721 has 12 divisors (see below), whose sum is σ = 298014340. Its totient is φ = 137410560.

The previous prime is 206216719. The next prime is 206216729. The reversal of 206216721 is 127612602.

It can be written as a sum of positive squares in 2 ways, for example, as 44036496 + 162180225 = 6636^2 + 12735^2 .

It is not a de Polignac number, because 206216721 - 2¹ = 206216719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (206216729) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19941 + ... + 28461.

Almost surely, 2^206216721 is an apocalyptic number.

It is an amenable number.

206216721 is a deficient number, since it is larger than the sum of its proper divisors (91797619).

206216721 is a wasteful number, since it uses less digits than its factorization.

206216721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11216 (or 11213 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 206216721 is about 14360.2479435419. The cubic root of 206216721 is about 590.8010960259.

The spelling of 206216721 in words is "two hundred six million, two hundred sixteen thousand, seven hundred twenty-one".