217931182561 has 9 divisors (see below), whose sum is σ = 227829644371. Its totient is φ = 208445643472.

The previous prime is 217931182549. The next prime is 217931182589. The reversal of 217931182561 is 165281139712.

The square root of 217931182561 is 466831.

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., 104054630625 + 113876551936 = 322575^2 + 337456^2 .

It is not a de Polignac number, because 217931182561 - 2¹¹ = 217931180513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217931182531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 10726965 + ... + 10747261.

Almost surely, 2^217931182561 is an apocalyptic number.

217931182561 is the 466831-st square number.

217931182561 is the 233416-th centered octagonal number.

It is an amenable number.

217931182561 is a deficient number, since it is larger than the sum of its proper divisors (9898461810).

217931182561 is an frugal number, since it uses more digits than its factorization.

217931182561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40640 (or 20320 counting only the distinct ones).

The product of its digits is 181440, while the sum is 46.

The spelling of 217931182561 in words is "two hundred seventeen billion, nine hundred thirty-one million, one hundred eighty-two thousand, five hundred sixty-one".