209656238799121 has 9 divisors (see below), whose sum is σ = 216637971749499. Its totient is φ = 202892699936400.

The previous prime is 209656238799053. The next prime is 209656238799131. The reversal of 209656238799121 is 121997832656902.

The square root of 209656238799121 is 14479511.

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

It can be written as a sum of positive squares in only one way, i.e., 44435036053521 + 165221202745600 = 6665961^2 + 12853840^2 .

It is not a de Polignac number, because 209656238799121 - 2²⁹ = 209655701928209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209656238799131) 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, 448631301 + ... + 449098381.

Almost surely, 2^{209656238799121} is an apocalyptic number.

209656238799121 is the 14479511-st square number.

209656238799121 is the 7239756-th centered octagonal number.

It is an amenable number.

209656238799121 is a deficient number, since it is larger than the sum of its proper divisors (6981732950378).

209656238799121 is an frugal number, since it uses more digits than its factorization.

209656238799121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 934224 (or 467112 counting only the distinct ones).

The product of its (nonzero) digits is 176359680, while the sum is 70.

The spelling of 209656238799121 in words is "two hundred nine trillion, six hundred fifty-six billion, two hundred thirty-eight million, seven hundred ninety-nine thousand, one hundred twenty-one".