210809520756961 has 81 divisors (see below), whose sum is σ = 256512862309977. Its totient is φ = 172739951455680.

The previous prime is 210809520756893. The next prime is 210809520757037. The reversal of 210809520756961 is 169657025908012.

The square root of 210809520756961 is 14519281.

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 4644262053025 + 206165258703936 = 2155055^2 + 14358456^2 .

It is not a de Polignac number, because 210809520756961 - 2²⁹ = 210808983886049 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (61).

It is a self number, because there is not a number n which added to its sum of digits gives 210809520756961.

It is not an unprimeable number, because it can be changed into a prime (210809520757961) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 229390120060 + ... + 229390120978.

It is an arithmetic number, because the mean of its divisors is an integer number (3166825460617).

Almost surely, 2^{210809520756961} is an apocalyptic number.

210809520756961 is the 14519281-st square number.

210809520756961 is the 7259641-st centered octagonal number.

It is an amenable number.

210809520756961 is a deficient number, since it is larger than the sum of its proper divisors (45703341553016).

210809520756961 is an frugal number, since it uses more digits than its factorization.

210809520756961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2048 (or 1024 counting only the distinct ones).

The product of its (nonzero) digits is 16329600, while the sum is 61.

The spelling of 210809520756961 in words is "two hundred ten trillion, eight hundred nine billion, five hundred twenty million, seven hundred fifty-six thousand, nine hundred sixty-one".