206287647721 has 9 divisors (see below), whose sum is σ = 219144215749. Its totient is φ = 194145813184.

The previous prime is 206287647679. The next prime is 206287647739. The reversal of 206287647721 is 127746782602.

The square root of 206287647721 is 454189.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 153487321 + 206134160400 = 12389^2 + 454020^2 .

It is not a de Polignac number, because 206287647721 - 2¹³ = 206287639529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (206287647421) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 7707855 + ... + 7734571.

Almost surely, 2^206287647721 is an apocalyptic number.

206287647721 is the 454189-th square number.

206287647721 is the 227095-th centered octagonal number.

It is an amenable number.

206287647721 is a deficient number, since it is larger than the sum of its proper divisors (12856568028).

206287647721 is an frugal number, since it uses more digits than its factorization.

206287647721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53468 (or 26734 counting only the distinct ones).

The product of its (nonzero) digits is 3161088, while the sum is 52.

The spelling of 206287647721 in words is "two hundred six billion, two hundred eighty-seven million, six hundred forty-seven thousand, seven hundred twenty-one".